JP2000214072A - Cantilever-type suction sensor and analytical method for suction force - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cantilever-type suction sensor whose sensitivity and reliability are high. SOLUTION: A thin film 2 and a thin film 3 whose materials are different from each other are formed on the surface and the backside of a cantilever 1. Then, when a suction substance such as a vapor, a gas or the like is sucked to the thin films 2, 3, their film tension is changed. By making use of a fact that the cantilever 1 is bent to the film whose tension is larger, its bend 7 is detected so as to be used as a humidity sensor or a gas sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to humidity, various gases,
The present invention relates to a sensor technology for detecting adsorption phenomena of ions and the like, charging and chemical reactions, or adsorption power of minute solids.

[0002]

2. Description of the Related Art
There are many adsorption-type sensors typified by a wet and dry bulb type hygrometer and a ceramic type sensor. Further, there is a method for measuring the amount of charge such as a zeta potentiometer. But,
In all of these, it is difficult to detect very low concentrations and trace amounts of an object. For example, there is practically no humidity sensor that can reliably detect humidity of 10% or less. On the other hand, there has been no method or sensor for directly measuring the adsorption force of a fine solid on a substrate.

An object of the present invention is to provide a cantilever-type adsorption sensor and a method for analyzing an adsorption force, which can solve the above-mentioned problems which have been difficult in the prior art, and have high sensitivity and reliability.

[0004]

The gist of the present invention will be described with reference to the accompanying drawings.

[0005] Thin films 2 and 3 of different materials are formed on the front and back surfaces of the cantilever 1, respectively. When an adsorbent 5 such as water vapor or gas is adsorbed on the thin films 2 and 3, the film tension changes. The present invention relates to an adsorption sensor characterized by using the fact that the cantilever 1 bends in the direction of larger tension and detects the bend 7 so that it can be used as a humidity or gas sensor.

Further, the cantilever 1 is formed so that the surface roughness differs between the surface and the back of the cantilever 1 so that the surface area differs.
When the adsorbate 5 such as water vapor or gas is adsorbed on the front surface or the back surface of the cantilever 1, the film tension of the cantilever 1 changes. The present invention relates to an adsorption sensor characterized in that it can be detected and used as a humidity or gas sensor.

Further, thin films 2 and 3 of different materials are formed on the front and back surfaces of the cantilever 1, respectively, or formed so that the surface roughness differs between the front and back surfaces of the cantilever 1 so that a difference in surface area occurs. The present invention relates to an adsorption sensor characterized in that a difference in adsorption and charge of an adsorbate 5 such as various ions is used on the surface or back surface of the cantilever 1 to detect a chemical change occurring on the front surface or back surface of the cantilever 1. It is.

Further, the tip of the cantilever 1 is brought into contact with a fine solid 10 adsorbed on a predetermined surface 9 such as a substrate surface,
Utilizing the adsorption of the micro solids 10 to the cantilever 1, the bending 7 of the cantilever 1 generated when the micro solids 10 are removed (pulled out) from the predetermined surface 9 is measured, and the force required at this time is detected. In the said minute solid
The cantilever 1 is analyzed by analyzing the attraction force of the
The present invention relates to an adsorption force analysis method characterized in that it is possible to cope with the analysis of solid materials having various adsorption powers by changing the material.

Further, a meniscus 11 in which water vapor is condensed is formed between the minute solid 10 and the cantilever 1,
The principle is to use the meniscus tension generated when the cantilever 1 separates to measure the adsorbing force of the micro solids 10. At this time, the meniscus shape is controlled by changing the ambient humidity to change the shape of the micro solids 10. The method according to claim 4, wherein the attraction force is measured.

The detection of the deflection 7 of the cantilever 1 is performed by using a detection means 4 such as an optical system using a laser differential amplifier, a non-contact capacitance change detection system, or a switch system using bending. The present invention relates to a cantilever-type adsorption sensor and an adsorption force analysis method according to any one of claims 1 to 5, characterized in that they are configured.

Further, the analysis of the adsorbed material 5 on the cantilever 1 and the adsorbing power of the fine solid 10 adsorbed on a predetermined surface 9 such as the substrate surface according to any one of claims 1 to 6 described above. A method for analyzing, characterized in that the cantilever 1 is vibrated at a resonance frequency in advance, and when adsorption occurs on the cantilever 1, the adsorption characteristic is analyzed as a change in resonance frequency and a phase change in vibration. The present invention relates to an adsorption force analysis method described above.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment (how to carry out the invention) of the present invention, which is considered to be the best, will be briefly described with reference to the drawings, showing its operational effects.

For example, when gas molecules and liquid molecules in the atmosphere are adsorbed on the surface of the thin film formed on the front surface and the back surface of the cantilever, they attract each other and tend to move due to aggregation. However, in reality, they cannot be easily moved because they are fixed to the surface of the thin film by adsorption. Therefore, a tension acts to attract each other to the adsorption layer (thin film). This tension affects, for example, the cantilever itself on which the thin film is formed, and a force acts to deflect the cantilever inward.

Further, since the size of the cantilever increases in proportion to the thickness of the adsorption layer (thin film), the bending of the cantilever increases.

In particular, if the cantilever is formed thin, the influence of the adsorbing layer increases, so that the cantilever can be largely bent by a small force of the adsorbing layer. Depending on the material of the adsorbing layer and the cantilever, the adsorbing layer may act to expand, and in this case, compressive stress acts to reverse the direction in which the cantilever bends. In the present invention, for example, different thin films 2 and 3 are formed on the front and back surfaces of the cantilever 1, respectively.
And the direction of the deflection are different. As a result, the cantilever 1 itself has a bending amount and a direction corresponding to the difference between the respective characteristics.

If this is measured by, for example, the non-contact type high-sensitivity optical detection means 4, the amount and direction of the deflection can be quantified. These are characterized in that they can be used in any environment, such as in a solution, various gas atmospheres, and in a vacuum, and the adsorbate 5 can have a very wide range of ions, gas molecules, water vapor, and a very small amount of charge or fine particles. It is a feature. Also, even when the cantilever 1 is made of the same material on the front and back surfaces, the surface is roughened so that the surface and the back surface have different surface areas,
By changing the suction area, it is possible to detect the difference in the bending 7 of the cantilever 1 due to the similar suction, and to obtain a suction sensor.

On the other hand, for example, when the minute solid 10 is adsorbed on a certain substrate 9, the minute solid 10 is adsorbed on the tip of the cantilever 1 and is pulled up from the substrate 9, and the bending 7 of the cantilever 1 at that time is reduced. By determining the force at the time of measurement and removal, the adsorption force can be quantified. This is also a detection method using the adsorption characteristics of the cantilever 1.

Further, in the ordinary atmosphere, a meniscus 11 is formed preferentially in a narrow space by condensation of water vapor. The meniscus 11 acts to attract objects sandwiching the meniscus 11 to each other, and is a large force.

Therefore, the tip of the cantilever 1 and the substrate 9
By utilizing the meniscus tension generated between the above micro solids 10 and pulling out with a force larger than the attraction force between the micro solid 10 and the substrate 9, the micro solid 10 is separated from the substrate 9, By quantifying the force required at that time,
The attraction force of the fine solid 10 on the substrate 9 can be measured.

Further, the cantilever 1 is set at the resonance frequency f [H
When the adsorbate 5 approaches or adheres to the front or back surface of the cantilever 1 while vibrating at z], the weight and the spring constant of the cantilever 1 change, so that the resonance frequency changes by Δf [Hz]. Also, cantilever 1
Is slightly shifted by Δθ.
These changes also occur when the tip of the cantilever 1 is attached to the substrate 9.

Therefore, by vibrating the cantilever 1 at the resonance frequency, the sensitivity of the adsorbed substance detection is greatly increased. This makes it possible to analyze a slight adsorption characteristic and realize a highly sensitive adsorption sensor. Even if the tip of the cantilever 1 approaches only the adsorbate 5 on the substrate 9, the same resonance frequency and phase change occur, so that the sensor can be a non-contact type adsorption force analysis sensor.

Various shapes can be used for the shape of the cantilever 1 described so far. For example, if a probe having a smaller radius of curvature is manufactured at the tip, the detection range can be localized. It is possible not only to improve the detection sensitivity but also to measure the distribution of the detection information in the plane of the substrate.

As described above, according to the present invention, the analysis of minute adsorbed substances is ensured. Until now, only a single change was used. However, since the present invention is of the operative type, it is a feature and an epoch-making feature that a small change can be reliably detected. In addition, since noise factors such as temperature, heat, vibration, and electric field are completely eliminated, the device can exert its power even in the danger of explosion and in environments that affect life. In addition, it can be manufactured in a very small size and is considered to have high versatility. It is possible to use cantilevers 1 of various shapes.

In particular, the inventions described in claims 1 to 3 are effective for various chemical reactions because the adsorption phenomenon on the thin film surface of the cantilever is changed into stress.

In particular, in the second aspect of the invention, the same effect can be obtained by changing the surface roughness even with the cantilever 1 of a single material, and it can be said that the structure is more practically effective.

It is very effective when it is necessary to know the difference in the reaction between the two types of surfaces.

In the invention according to claim 4, the analysis and control of the adsorption force of minute solids is important in the future in the field of industry such as electronic devices and liquid crystal display devices and in the future development of technologies such as quantum effect devices. It becomes practical.

Further, the invention according to claim 5 is effective for fine solids that are always adsorbed with a weak adsorption force, and is very effective for fine processing.

Further, since the meniscus is easily and surely generated between the solids, use of the meniscus increases versatility.

According to the seventh aspect of the present invention, as described above, by vibrating the cantilever at the resonance frequency, the sensitivity of detecting the adsorbed substance is greatly increased. This makes it possible to analyze a slight adsorption characteristic and realize a highly sensitive adsorption sensor. Further, even if the tip of the cantilever approaches only the adsorbate on the substrate, the same resonance frequency and phase change occur, so that the sensor can be a non-contact type adsorption force analysis sensor.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the suction sensor according to the first and third aspects.

FIG. 1A shows an example in which gold films 2 are formed on both surfaces of a cantilever 1 as an example for comparison with this embodiment, and FIG. 1B shows a silicon nitride film on one of the surfaces. Membrane 3
Are shown, and two examples are shown.
The smaller the size of the cantilever 1, the higher the detection sensitivity. For example, in this case, one having a length of 200 μm, a thickness of 20 μm, and a spring constant of several N / m can be used. At the time of detecting the adsorbate 5, the bending 7 of the cantilever 1 is measured by using the laser optical system 4 as the detecting means 4. As shown in FIG. 2, when the adsorbents 5 such as water vapor, gas, and ions are adsorbed on the surface of the cantilever 1, a force acts so as to coagulate, and the cantilever 1 tends to bend. At this time, as shown in FIG. 3, the bending 7 occurs due to the difference in the adsorption characteristics between the both surfaces of the cantilever 1, and the cantilever 1 has a sensor function. FIG. 4 shows a change in atmospheric humidity measured using this sensor. When the gold film 2 and the silicon nitride film 3 are formed on the cantilever 1,
The flexure 7 occurs in the lever 1 due to the difference in the adsorption characteristics depending on the material, indicating that the humidity change can be measured with extremely high sensitivity. On the other hand, when the gold films 2 are formed on both surfaces of the cantilever 1, it can be seen that there is almost no effect on the humidity change. These facts indicate that the reliability of the humidity sensor is high.

FIG. 5 shows an example in which one surface of the cantilever 1 is adhered to the fine solid 10 adhered on the substrate 9 (predetermined surface 9) according to claim 4 to form an adsorption sensor. As described above, only the selected minute solid 10 can be pulled out from the substrate surface 9 by the attraction force of the cantilever 1. FIG. 6 shows a change in the sensor suction force when the tension due to the meniscus 11 between the cantilever 1 and the minute solid 10 is changed according to claim 5. By utilizing this, it becomes possible to pull out the minute solid 10 adsorbed on the solid. FIG.
Shows an example in which the adsorption area is changed by changing the surface roughness of the front and back surfaces of the cantilever 1 based on claim 2.

FIGS. 8 and 9 show that the meniscus 11 formed between the cantilever 1 and the micro solid 10 is used to reduce the meniscus 11 by lowering the humidity, and the micro solid 10 is collapsed or pulled out by itself. It is shown that.

[0036]

Since the present invention is constructed as described above, it provides a cantilever type adsorption sensor and a method for analyzing an adsorption force, which have high sensitivity and reliability.

That is, as described above, according to the present invention, the analysis of minute adsorbed substances is ensured. Until now, only a single change was used. However, since the present invention is of the operative type, it is a feature and an epoch-making feature that a small change can be reliably detected. In addition, since noise factors such as temperature, heat, vibration, and electric field are completely eliminated, the device can exert its power even in the danger of explosion and in environments that affect life. In addition, it can be manufactured in a very small size and is considered to have high versatility.

In particular, in the first to third aspects of the present invention, since the adsorption phenomenon on the surface of the thin film of the cantilever is changed into stress, it is effective for various chemical reactions.

In particular, in the second aspect of the invention, the same effect can be obtained by changing the surface roughness even with a cantilever made of a single material, and it can be said that the structure is more effective.

Also, it is very effective when it is necessary to know the difference in the reaction between two types of surfaces.

Further, in the invention according to claim 4, the analysis and control of the adsorption force of a minute solid is important in the future in the development of industries such as electronic devices and liquid crystal display devices and future technology such as quantum effect devices. It becomes practical.

Further, the invention according to claim 5 is effective for fine solids that are always adsorbed with a weak adsorption force, and is very effective for fine processing.

In addition, since the meniscus is easily and reliably generated between the solids, the versatility is enhanced by using the meniscus.

According to the sixth aspect of the present invention, the amount of deflection can be easily and reliably measured.

According to the seventh aspect of the present invention, by vibrating the cantilever at the resonance frequency, the sensitivity of detecting the adsorbed substance is greatly increased. This makes it possible to analyze a slight adsorption characteristic and realize a highly sensitive adsorption sensor. Further, even if the tip of the cantilever approaches only the adsorbate on the substrate, the same resonance frequency and phase change occur, so that the sensor can be a non-contact type adsorption force analysis sensor.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cantilever of the present embodiment.

FIG. 2 is an explanatory view showing a state of adsorption and aggregation on a cantilever.

FIG. 3 is an explanatory diagram showing a change in bending due to adsorption and aggregation of water vapor on a cantilever according to the present embodiment.

FIG. 4 is a graph showing the humidity dependence of the amount of deflection of the cantilever of the present embodiment.

FIG. 5 is an explanatory diagram showing a method for measuring an adsorbing force of a fine solid adsorbed on a substrate according to the present embodiment.

FIG. 6 is an explanatory diagram showing a method of measuring an attraction force using a meniscus generated between a cantilever and a fine solid according to the present embodiment.

FIG. 7 is an explanatory view showing cantilevers having different surface roughness according to the present embodiment.

FIG. 8 is an explanatory diagram showing an attraction force measurement method w (collapse method) using the fact that the meniscus tension changes with humidity in the present embodiment.

FIG. 9 shows an adsorption force measurement method w (pulling-down method) using the fact that the meniscus tension changes with humidity in this example.
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cantilever 2 Thin film 3 Thin film 4 Detecting means 5 Adsorbed substance 7 Bending / bending 9 Predetermined surface 10 Micro solid 11 Meniscus

Claims (7)

[Claims] 1. A thin film of a different material is formed on each of a front surface and a back surface of a cantilever. When an adsorbate such as water vapor or gas is adsorbed on the thin film, the film tension changes. An adsorption sensor characterized by using the fact that this cantilever bends and detecting this bend so that it can be used as a humidity or gas sensor. 2. The cantilever is formed so that the surface roughness differs between the front surface and the back surface of the cantilever so that a difference in surface area occurs. When an adsorbate such as water vapor or gas is adsorbed on the front surface or the back surface of the cantilever, An adsorption sensor characterized by using the fact that the cantilever bends to the side with higher tension due to a change in the membrane tension, and detects this bend so that it can be used as a humidity or gas sensor. 3. A thin film of a different material is formed on each of the front and back surfaces of the cantilever or the surface roughness of the cantilever is made different from the surface roughness of the cantilever so that a difference in surface area occurs. Alternatively, an adsorption sensor characterized by detecting a chemical change occurring on the front surface or the back surface of the cantilever by utilizing the difference between the adsorption and the charging of adsorbed substances such as various ions on the back surface. 4. The method according to claim 1, wherein the tip of the cantilever is brought into contact with a micro solid adsorbed on a predetermined surface such as a substrate surface, and the micro solid is adsorbed to the cantilever by utilizing the adsorption of the micro solid to the cantilever. By measuring the bending of the cantilever generated when removing (pulling out), detecting the force required at this time, analyzing the adsorbing force of the micro solid on a predetermined surface, and changing the material of the cantilever, various suction An adsorption force analysis method characterized by being able to cope with the analysis of a solid material having a force. 5. In principle, a meniscus in which water vapor is condensed is formed between the micro solid and the cantilever, and the adsorption force of the micro solid is measured using a meniscus tension generated when the cantilever separates. 5. The method according to claim 4, wherein at this time, the meniscus shape is controlled by changing the ambient humidity to measure the attraction force of the fine solid. 6. The method according to claim 1, wherein the bending of the cantilever is detected by a detecting means such as an optical system using a laser differential amplifier, a non-contact capacitance change detecting system, or a switch system using bending. The cantilever type adsorption sensor and adsorption force analysis method according to any one of claims 1 to 5, characterized in that: 7. A method for analyzing an adsorbed substance to a cantilever according to any one of claims 1 to 6, and analyzing an adsorption force of a minute solid adsorbed on a predetermined surface such as the substrate surface. A method for analyzing an attraction force, characterized in that the cantilever is vibrated in advance at a resonance frequency, and when the cantilever is adsorbed, the adsorption characteristic is analyzed as a change in resonance frequency and a phase change in vibration. .