JPH08130219A - Fine structure forming method and its equipment - Google Patents

Abstract

PURPOSE: To form fine structure excellent in controllability, stability and reproducibility, by using the tip of a pointed pin similarly to STM, without using a tunnel current or the like under a high electric field. CONSTITUTION: A pin 1 whose tip is covered with liquid (or liquid metal) 3 is made to approach a substrate 2, and brought into contact with the substrate 2, via the liquid 3. In this state, the substrate surface is scanned with the pin 1, and the liquid 3 is transferred on the substrate 2. Thereby a thin line 4 is formed on the substrate 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new fine structure manufacturing method and an apparatus for realizing the same.

[0002]

2. Description of the Prior Art Conventionally, a scanning tunneling electron microscope (hereinafter referred to as ST
A number of microfabrications and atom manipulations using M) have been reported. However, since these are all processing of a solid substrate with a solid needle, the tunnel current from the needle and the needle current without contacting the substrate can be used. The focus was on methods and devices for processing using a locally high electric field.

[0003]

However, in the method of processing using a tunnel current from the needle or a local high electric field without bringing the needle and the substrate into contact with each other, the periphery of the needle is locally exposed to an extremely high electric field. However, there was a problem in stability and reproducibility such as the tip shape of the needle gradually changing.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to utilize a sharp needle tip as in the STM while maintaining a high level as in the prior art. It is an object of the present invention to provide a fine structure manufacturing method and a device capable of forming a fine structure without utilizing a tunnel current or the like under an electric field, excellent in controllability, stable and highly reproducible.

[0005]

In order to achieve the above object, the invention according to claim 1 makes a needle whose tip is covered with liquid or liquid metal is brought close to a substrate, and the needle and the substrate are liquid or liquid metal. It is characterized in that a fine structure is produced while the liquid or liquid metal is transferred from the needle to the substrate by realizing the state of contact via the needle and scanning the needle in this state. A second aspect of the present invention is a crucible having a structure in which a needle is provided at a lower portion and a liquid or liquid metal that is well compatible with the material of the needle is accommodated therein, and the liquid or liquid metal is transmitted to the needle. A scanning unit for moving the needle or the needle and the crucible in three directions of X, Y, and Z; and a stage on which a substrate is placed. The needle is brought into contact with the substrate through the liquid or liquid metal. Scanning the needle or the needle and the crucible to transfer a liquid or liquid metal onto the substrate to form a fine structure. According to a third aspect of the invention, in the second aspect of the invention, the crucible is provided with a temperature control means. The invention according to claim 4 is the invention according to claim 2 or 3.
In the invention described in (3), the stage is equipped with a temperature control means.

[0006]

In the invention described in claims 1 and 2, the liquid or liquid metal transmitted through the needle comes into contact with the substrate. Since the needle and the substrate are in contact with each other with the liquid or liquid metal sandwiched between them, damage to the needle such as measurement of resistance (or conductance) under normal electric field or measurement of unique force of liquid due to surface tension or viscosity It is possible to easily control the contact state between the liquid or the liquid metal and the substrate by no measurement.
In addition, since the one that makes contact between the substrate and the needle is liquid or liquid metal, it is possible to scan the needle while controlling the contact state between the liquid or liquid metal and the substrate constant without damaging the needle tip or the like. Is. If the material, temperature of the needle, liquid or liquid metal, and substrate are set appropriately, the desired amount of liquid or liquid metal can be transferred from the needle to the substrate as if writing a fountain pen to the microstructure. Can be formed. Therefore, unlike the prior art, it is not necessary to apply a high electric field to the needle tip, and the fine structure can be formed without the solid needle and the substrate coming into direct contact with each other. In the invention of claim 3, the temperature control means controls the temperature of the crucible to facilitate the transfer of the liquid or the liquid metal to the needle. In the invention of claim 4, the liquid or liquid metal transmitted from the needle to the substrate is maintained in a good liquid state by controlling the temperature of the stage by the temperature control means.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a schematic view of a tip portion of a needle showing a method for producing a fine structure according to the present invention, in which a liquid (or a liquid metal) transmitted through the needle is transferred onto a substrate and fine lines are formed by scanning the needle. Show the situation. In the figure, 1 is a needle, 2 is a substrate, 3 is a liquid (or liquid metal), and 4 is a fine line as a fine structure formed on the substrate 2. In this embodiment, the needle 1 is a metal such as tungsten (W) and the liquid 3 is a liquid metal that has been appropriately heated (for example, liquid gallium), but the same applies to various liquids or combinations of liquid metal and needle. The process is possible. There are various ways of transmitting the liquid 3, such as a type in which the liquid 1 covers the entire needle 1, a type in which a groove is formed up to the middle of the needle 1 and the liquid 3 flows along the groove, and a fine pattern is formed in the center of the needle 1. A type in which a transparent hole is formed and the liquid metal 3 flows therethrough can be considered.

FIG. 2 is a view showing a fine structure produced by carrying out the method of the present invention, which is a sectional view taken along a direction perpendicular to a fine line.

FIG. 2A shows an example of a metal thin wire formed on a metal substrate. The substrate 2 is composed of a semiconductor substrate 2-2 and a W thin film 2-1 formed on the semiconductor substrate 2-2. A thin wire 4 of gallium (Ga) is formed on the surface of the metal 1. This thin line 4
Can be obtained by scanning the needle while flowing the liquid Ga over the W thin film 2-1. The size of the thin wire 4 can be controlled by the temperature of the liquid Ga, the substrate temperature, the distance between the needle and the substrate, the scanning speed, and the like. The narrow line width is 2 to 3 nm, and the wide line width is about 100 nm. The thickness can also be controlled within the range of the thickness of a monoatomic layer to several tens of atomic layers depending on the conditions. The higher the substrate temperature, the better the liquid state can be maintained, but if the temperature is too high, the atoms of the liquid metal migrate on the substrate 2 and a fine pattern spreads. On the other hand, if the substrate temperature is too low, the viscosity of the liquid metal increases and scanning cannot be performed properly. Therefore, the substrate temperature needs to be set to an appropriate value. In this embodiment, the substrate temperature is about 80 ° C., and the liquid state is maintained under the needle by the heat transmitted through the needle, but the fine pattern placed on the substrate 2 solidifies as the needle moves away. It is set to the condition to go.

FIG. 2 (b) is a view showing an embodiment in which the method of the present invention is used to form a semiconductor thin wire. Substrate 2 is GaAs
2-4 and AlGaAs 2-3 formed thereon. First, the Ga thin wire 4 is formed on the AlGaAs 2-3 by the same method as described above. Thickness is 3
Conditions such as the substrate temperature are set so that the atomic layer or less is obtained.
After the thin Ga line 4 is formed, the substrate temperature is raised while exposing the whole to the atmosphere of As. If Ga is 3 atomic layers or less, As completely penetrates into Ga to form GaAs. The upper GaAs thin wire 4-1 is completed (FIG. 2 (c)).

FIG. 3 is a schematic block diagram of an apparatus for realizing the method of the present invention. In the figure, 5 is a crucible having a needle 1 provided at the bottom thereof. The crucible 5 contains a liquid (or liquid metal) 3 inside, and has a heater 7 as a temperature control means on the outer peripheral surface, The unit 8 is configured to be finely moved independently in three directions of X, Y, and Z to precisely control the position. The portion of the crucible 5 and the needle 1 has a mechanism similar to that of the liquid metal ion source of the focused ion beam implanter. Crucible 5
The liquid 3 therein comes out from a hole formed in the lower portion of the crucible 5 and is transmitted to the needle 1. Needless to say, the needle 1 and the liquid 3 should be a combination that is well compatible with each other and that the liquid 3 does not erode the needle 1, but there are many such combinations as is known in the liquid metal ion source. The crucible 5 thus configured is attached to the needle portion such as STM. Reference numeral 9 denotes a substrate stage disposed below the crucible 5, which is coarsely moved independently in three directions of X, Y and Z, and is provided with a heater 10 as a heating means and is provided on the upper surface. The substrate 2 is placed. Reference numeral 11 is a control unit for controlling the scanning unit 8, the stage 9 and the heaters 7 and 10. In this case, although the needle 1 and the crucible 5 are integrally moved in the present embodiment, the crucible 5 may be fixed and only the needle 1 may be moved in three directions. Further, in this embodiment, the needle 1 is formed of W, and G
The liquid metal 3 of a is contained in the crucible 5.

In the present apparatus, first, after determining the position for forming the fine line, the needle 1 is moved together with the crucible 5 in the Z direction and gradually lowered. At some point, the liquid metal 3 of Ga contacts the substrate 2 and
Spread to the side. This can be detected by an abrupt change in resistance (or conductance) or an abrupt change in liquid-specific force due to surface tension or viscosity, as described later. After a while
The needle 1 is gradually raised in the Z direction to set the size of the constricted portion of the liquid metal 3 to a desired value, and thereafter, the needle 1 is scanned while keeping this value constant, and the fineness corresponding to the movement of the needle 1 is set. The structure is formed on the substrate 2. A fine line with high uniformity can be formed although the disorder remains at the beginning of writing the fine line.

In the method of the present invention, it is important to properly select the substrate temperature as described above, but the migration of atoms in the liquid state on the substrate is severe and the substrate heater 1
It is conceivable that even if the uniform heating by 0 occurs, a fine structure cannot be formed with good controllability. However, also in this case, the substrate temperature is set to a low temperature at which the liquid metal 3 is sufficiently solidified, and a laser beam or an electron beam is moved in accordance with the scanning of the needle 1 to keep only the vicinity of the needle 1 in a good liquid state. This can be handled by adding a mechanism for heating to a temperature that can be maintained to this device.

Finally, the control of the contact state between the liquid metal and the substrate in this embodiment will be described. FIG. 4 is a diagram showing a change in conductance between the needle 1 and the substrate 2 measured at a low voltage when it is desired to raise the needle 1 after bringing the liquid Ga3 into contact with the tungsten needle 1. Since the cross section just before the liquid Ga3 is broken is so small that the quantum effect becomes remarkable, the change of the conductance is not smooth, and a step structure is observed. The dotted line is the liquid Ga estimated from this step structure.
It is the number of atoms in the most constricted part of 3. A region where conductance can usually be easily measured (for example, 1000 μS = 1
It can be seen that the size of the constriction can be easily controlled by the dimension of atomic order by measuring with KΩ). Therefore, by scanning the needle 1 while monitoring the conductance, the needle 1 can be scanned while controlling the size of the constriction on the atomic order, and as a result, a fine line controlled on the atomic order is realized.

When the substrate is non-conductive, a liquid-specific force due to surface tension or viscosity can be used instead of electrical measurement. The liquid exerts a force in the direction of attracting the needle and the substrate to each other, the size of which corresponds to the size of the neck.
Therefore, if this force is measured based on the principle of the atomic force microscope, the size of the constriction can be precisely controlled as in the conductance measurement.

[0016]

As described above, according to the method for producing a fine structure according to the present invention, the fine structure can be formed by utilizing the liquid or liquid metal that travels through the needle while utilizing the pointed tip of the needle as in the STM. Since the needle and the substrate are always in contact with each other with the liquid or liquid metal sandwiched between them, the contact state between the substrate and the liquid or liquid metal is controlled by normal low voltage resistance (or conductance) measurement. In addition, since the space between the needle and the substrate is liquid or liquid metal, there is no risk of damaging the needle tip even if the needle is scanned, excellent controllability, and stable and reproducible microfabrication can be achieved. . Further, in the fine structure forming apparatus according to the present invention, the contact area of the liquid or liquid metal and the substrate can be controlled in atomic order,
As a result, there is an effect that a fine structure controlled on an atomic order can be formed. Further, unlike the conventional STM processing, by controlling the substrate temperature, the crucible temperature, the distance between the needle and the substrate, the scanning speed, etc., the width of the thin line can be controlled in a wide range from several atoms to several hundred atoms with the same method and device. There is also the effect that you can select.

Further, the method and apparatus according to the present invention can be used not only for forming a metal fine structure by using a liquid metal, but also for application to a semiconductor fine structure as in the embodiment. Further, by using various kinds of liquids or liquid metals and materials that react with them, it is possible to apply to the formation of fine structures of many materials.

[Brief description of drawings]

FIG. 1 is a schematic view showing a fine structure manufacturing method according to the present invention.

FIG. 2A is a cross-sectional view of the first embodiment of the present invention,
(B) is sectional drawing of a 2nd Example, (c) is sectional drawing of a 2nd Example.

FIG. 3 is a schematic configuration diagram of a fine structure manufacturing apparatus according to the present invention.

FIG. 4 is a diagram showing a change in conductance due to a change in needle position (Z direction) measured by a fine structure manufacturing apparatus.

[Explanation of symbols]

1 ... Needle, 2 ... Substrate, 2-1 ... Tungsten, 2-2 ... Semiconductor substrate, 2-3 ... AlGaAs thin film, 2-4 ... GaA
s substrate, 3 ... liquid (or liquid metal), 4 ... fine wire, 5 ...
Crucible, 7 ... Heater, 8 ... Scanning unit, 9 ... Stage, 10 ... Heater, 11 ... Control unit.

Claims (4)

[Claims] 1. A liquid or a liquid metal covers a tip of the needle close to a substrate to realize a state in which the needle and the substrate are in contact with each other through the liquid or the liquid metal, and by scanning the needle in this state, A method for producing a fine structure, which comprises producing a fine structure while transferring a liquid or a liquid metal from a needle to a substrate. 2. A crucible having a needle at a lower portion thereof, a liquid or liquid metal that is well adapted to a material of the needle is accommodated therein, and the liquid or the liquid metal is configured to be transmitted to the needle, and the needle or the crucible. A scanning unit for moving the needle and the crucible in three directions of X, Y, and Z, and a stage on which a substrate is placed are provided, and the needle is brought into contact with the substrate via the liquid or liquid metal, A fine structure manufacturing apparatus characterized by scanning a needle and a crucible to transfer a liquid or a liquid metal onto the substrate to manufacture a fine structure. 3. The fine structure manufacturing apparatus according to claim 2, wherein the crucible is provided with a temperature control means. 4. The fine structure manufacturing apparatus according to claim 2, wherein the stage has a temperature control means.