JP2586401B2 - Metal atom pattern forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal atom pattern formed of a metal single atom adsorption layer on the surface of a semiconductor substrate.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices, for example, the width of a metal pattern has become extremely narrow. For some purposes, a metal pattern having a width of an atomic size is also required. As one method for achieving such an object, the inventor of the present invention disclosed in Japanese Patent Application Laid-Open No. Hei 3-207862 (Japanese Patent Application No. 2-3095) previously filed by the present inventors discloses a scanning tunneling microscope.
Scope (STM) was proposed.

Referring to FIG. 3, which is a schematic cross-sectional view of a step of forming a metal atom pattern, the method of forming a metal atom pattern described in the above-mentioned publication is as follows.

First, the surface of a substrate 201 placed in a vacuum vessel (not shown) containing an STM (not shown)
^Purified in ultra-high vacuum of the order of ^-8 Pa. Thereafter, under a predetermined ultra-high vacuum (a degree of vacuum lower than 10 ⁻⁸ Pa), a metal halide gas 231 formed by combining the halogen ions 213 and the metal ions 222 is introduced into the vacuum vessel. At this time, a part of the metal halide gas 231 is adsorbed on the surface of the substrate 201, and a metal halide single molecule adsorption layer 235 is formed on the surface of the substrate 201.
(A)].

In this state, the STM needle 202 is
The desired position on the surface is approached. The distance between the tip of the needle 202 and the surface of the substrate 201 is several angstroms. A voltage is applied between the needle 202 and the substrate 201 so that the needle 202 becomes positive, and a minimal electric field 203 is formed between the tip of the needle 202 and the surface of the substrate 201. This minimal electric field 203
Is decomposed by this minimal electric field 203, gasified halogen ions 212 are desorbed, and metal atoms 221 remain [FIG.
(B)]. After the needle 202 scans within the range of the desired position, the introduction of the metal halide gas 231 is stopped, and the metal halide gas 231 and the halogen ions 212 remaining floating in the vacuum vessel are exhausted out of the vacuum vessel. You.
Further, the substrate 201 is heated to a predetermined temperature,
The metal halide monomolecular adsorption layer 235 remaining on the surface is gasified to become a metal halide gas, and the metal atoms 221
Is formed.

[0006]

In the metal atom pattern forming method described in the above publication, the removal of the metal halide monomolecular adsorption layer from the substrate surface is performed by heating the substrate. However, due to this heating, some of the metal atoms constituting the metal atom pattern are gasified and desorbed from the substrate, and some of them cause a temperature drift. As a result, the initially formed metal atom pattern (having a desired shape) tends to collapse, and it becomes difficult to form a metal atom pattern having a desired shape.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for forming a metal atom pattern with high precision, stability, and extremely simple steps for each metal atom.

[0008]

According to the metal atom pattern forming method of the present invention, a halogen single atom adsorption layer comprising halogen atoms is formed on a surface of a semiconductor substrate maintained at a predetermined temperature under a predetermined degree of vacuum. Performing a step of desorbing the halogen atoms at a plurality of desired positions of the halogen single atom adsorption layer by electric field evaporation using a scanning tunneling microscope, and forming a halogen atom pattern on the surface of the semiconductor substrate. Metal atoms having a higher reactivity than the semiconductor substrate with respect to the halogen atoms are deposited on the surface of the semiconductor substrate, and the metal atoms are adsorbed at the desired positions on the semiconductor substrate surface, so that the metal atoms are moved to these desired positions. A metal atom pattern consisting of a monoatomic adsorption layer of metal atoms is formed. The formation of the metal halide gas by reaction with atoms and a step of removing the halogen atom pattern from the semiconductor substrate surface.

Preferably, the semiconductor substrate is silicon,
It is made of germanium, silicon-germanium alloy or compound semiconductor. More preferably, the halogen atom comprises fluorine, chlorine or bromine, and the metal atom comprises aluminum, cobalt, nickel, copper or zinc.

[0010]

Next, the present invention will be described with reference to the drawings.

Referring to FIG. 1, which is a schematic view of the structure of a pattern forming apparatus, an STM used in an embodiment of the present invention is shown.
Is formed as follows.

An STM is provided in a vacuum vessel 1 that can be evacuated to an ultra-high vacuum of the order of 10 ⁻⁸ Pa. This STM
Is mainly composed of a needle 102, a piezoelectric element 2 and a stage 3. A silicon substrate 101, which is a semiconductor substrate, is mounted on the stage 3, and the stage 3 can be cooled and heated to a predetermined temperature. The needle 102 is made by mechanically polishing platinum-iridium (Pt-Ir).
This needle 102 is connected to the piezoelectric element 2. Needle 102
The position (relative to three dimensions) with respect to the stage 3 (silicon substrate 101) is performed by three-dimensional movement of the piezoelectric element 2 by an electric control system 4 provided outside the vacuum vessel 1. The application of a voltage between the needle 102 and the silicon substrate 101 (stage 3) is also performed via the electric control system 4. The semiconductor substrate is not limited to silicon, and may be germanium, a silicon-germanium alloy, or a compound semiconductor.

The above-described vacuum vessel 1 is connected to the vacuum vessel 1 through a valve 6.
A chlorine gas, which is a halogen gas, is introduced. The introduction of the chlorine gas is performed from the liquid chlorine 7 stored in the gas storage chamber 6. The halogen gas introduced into the vacuum vessel 1 is not limited to chlorine gas, but may be fluorine gas or bromine gas. When fluorine gas is introduced into the vacuum vessel 1, liquid fluorine is stored in the gas storage chamber 6 instead of liquid chlorine 7. When bromine gas is introduced into the vacuum container 1, a container having a heating means is used instead of the gas storage chamber 6, and bromine which forms a liquid phase at normal temperature and normal pressure is stored in this container. I have. Aluminum is vapor-deposited on the silicon substrate 101 by the vapor deposition device 8 connected to the vacuum vessel 1. Silicon substrate 10
The metal deposited on 1 is not limited to aluminum, but it is sufficient that the reactivity of the metal atom to the halogen atom is higher than the reactivity of the semiconductor substrate (such as a silicon substrate) to the halogen atom. , Copper or zinc.

Referring to FIG. 1 and FIG. 2 which is a schematic cross-sectional view of the step of forming a metal atom pattern, the method of forming a metal atom pattern according to the above embodiment is as follows.

First, the silicon substrate 101 is placed on the stage 3, and the vacuum vessel 1 is evacuated to an ultra-high vacuum of the order of 10 ⁻⁸ Pa. In this ultrahigh vacuum state, the silicon substrate 101 is heated to about 1250 ° C. (via the stage 3), and the surface of the silicon substrate 101 becomes an extremely clean surface (by this heating and cleaning). After the silicon substrate 101 is cooled down to about room temperature, the degree of vacuum of the vacuum vessel 1 is set to the order of 10 ⁻⁷ Pa, and chlorine gas is flowed for several tens of seconds. As a result, a halogen single atom adsorption layer 115 composed of chlorine atoms 111 is formed on the silicon substrate 101 [FIG. 2 (a), FIG. 1].

Next, by using the electric control system 4, the needle 102 is
With the voltage applied to the needle 102, the needle 102
Is brought closer to a desired position on the surface of the silicon substrate 101. When the distance between the desired position on the surface of the silicon substrate 101 and the needle 102 is about 2 nm, a (tunnel) current starts to flow rapidly. At this interval, a pulse voltage at which the needle 102 becomes plus 6 V is applied to the silicon substrate 101 (using the electric control system 4). With this pulse voltage, a minimal electric field 103 is formed between a desired position on the surface of the silicon substrate 101 and the needle 102. Due to this minimal electric field 103, one chlorine atom 111 constituting the halogen single atom adsorption layer 115 at a desired position on the surface of the silicon substrate 101 is (approximately) subjected to electric field evaporation to form one chlorine ion 112 to form a silicon substrate 112. The chlorine ions 112 are desorbed from the surface 101 and are exhausted. Needle 1 (using electric control system 4)
02 scans the surface of the silicon substrate 101, and the above operation is repeated at each desired desired position on the surface of the silicon substrate 101. By this series of operations, a halogen atom pattern 116 formed by desorption of the chlorine atom 111 at each desired position is drawn (FIGS. 2B and 1).

The surface of the silicon substrate 101 and the needle 102
When the needle 102 is applied to the silicon substrate 101 at about plus 1 V at an interval of about 2 nm, a minimal electric field corresponding thereto is formed. In this case, the chlorine atom 1
No electric field evaporation and desorption from the surface of the silicon substrate 101 occur. On the other hand, when a pulse voltage of, for example, about 8 V is applied at the time of applying the pulse voltage, the minimal electric field greatly spreads from a desired position, and a plurality of chlorine atoms are applied once around one chlorine atom at the desired position. By the operation described above, it is desorbed from the surface of the silicon substrate, and it becomes difficult to form a pattern having an atomic level accuracy.

Subsequently, aluminum atoms 121 are deposited on the surface of the silicon substrate 101 having the halogen atom pattern 116 by using the vapor deposition device 8. The surface of the silicon substrate 101 is covered with aluminum atoms 121 substantially consisting of one atomic layer [FIG. 2 (c), FIG. 1]. The electronegativity of aluminum is greater than the electronegativity of silicon, and the difference in electronegativity between chlorine and aluminum is greater than the difference in electronegativity between chlorine and silicon. For this reason, when aluminum atoms 121 are vapor-deposited directly on the surface of the halogen atom pattern 116 composed of chlorine atoms 111, the chlorine atoms 111 and the aluminum atoms 121 are ionized at those portions, and chlorine ions 113 (however, the chlorine ions 113 A metal halide gas 131 composed of approximately three chlorine ions and aluminum ions 122 is desorbed from the surface of the silicon substrate 101 and exhausted. As a result, the halogen atom pattern 116 is self-lifted off, and a metal atom pattern 125 composed of a single layer of aluminum atoms 121 is formed on the surface of the silicon substrate 101 where the halogen atom pattern 116 was not formed. [FIG. 2 (d), FIG. 1].

As described above, according to the present embodiment, the metal atom pattern 12 can be formed with a simple process with the accuracy of each atom.
5 can be formed. Further, since high-temperature treatment is not required in the process of forming the metal atom pattern 125 according to the present embodiment, the metal atom pattern 125 is not deformed or collapsed. Will not exist.

In the above embodiment, the halogen atom pattern is composed of chlorine atoms. However, when the halogen atom pattern is composed of fluorine atoms or bromine atoms, the formation of a halogen single atom adsorption layer is performed as follows. It is preferable to maintain the temperature of the silicon substrate (stage) from the time until the formation of the metal atom pattern. If the halogen atom pattern is composed of fluorine atoms, the silicon substrate (stage) is -10 because fluorine is more chemically active than chlorine.
It is preferable to cool to about 0 ° C. On the other hand, when the halogen atom pattern is composed of bromine atoms, the silicon substrate (stage) is preferably heated to a predetermined temperature because bromine is chemically more inert than chlorine.

[0021]

As described above, according to the metal atom pattern forming method of the present invention, it is possible to form a metal atom pattern with high precision, stability and extremely simple steps for each metal atom. Easy.

[Brief description of the drawings]

FIG. 1 is a schematic view of a configuration of a pattern forming apparatus used in an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a forming process of the embodiment.

FIG. 3 is a schematic cross-sectional view of a conventional step of forming a metal atom pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Piezoelectric element 3 Stage 4 Electric control system 5 Gas storage room 6 Valve 7 Liquid chlorine 8 Evaporation apparatus 101 Silicon substrate 102, 202 Needle 103, 203 Minimal electric field 111 Chlorine atom 112, 113 Chloride ion 115 Halogen single atom adsorption layer 116 Halogen atom pattern 121 Aluminum atom 122 Aluminum ion 125 Metal atom pattern 131,231 Halogen metal ion 201 Substrate 212,213 Halogen ion 221 Metal atom 222 Metal ion 235 Halogen metal monolayer adsorption layer

Claims (3)

(57) [Claims] A step of forming a halogen single atom adsorption layer made of halogen atoms on a surface of a semiconductor substrate kept at a predetermined temperature under a predetermined degree of vacuum, and by performing field evaporation using a scanning tunneling microscope. A step of desorbing the halogen atoms at a plurality of desired positions of the halogen single atom adsorption layer and leaving a halogen atom pattern on the surface of the semiconductor substrate, and having a higher reactivity with respect to the halogen atoms than the semiconductor substrate. A metal atom comprising a monoatomic adsorption layer of the metal atom at each of the desired positions by depositing metal atoms having the metal atoms on the surface of the semiconductor substrate and adsorbing the metal atoms at the desired positions on the surface of the semiconductor substrate. Forming a pattern, and forming a metal halide gas by the reaction of the halogen atoms and the metal atoms constituting the halogen atom pattern. Metal atom pattern forming method characterized in that the surface of the semiconductor substrate and a step of removing the halogen atom pattern. 2. The method according to claim 1, wherein the semiconductor substrate is made of silicon, germanium, a silicon-germanium alloy, or a compound semiconductor. 3. The metal atom pattern formation according to claim 1, wherein said halogen atom is made of fluorine, chlorine or bromine, and said metal atom is made of aluminum, cobalt, nickel, copper or zinc. Method.