JP2737613B2 - Method of forming fine pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a fine structure using an inert layer mask at the atomic layer level and mask pattern drawing by an electron beam, and relates to the fabrication of next-generation semiconductor elements and new functional devices. Things.

[0002]

2. Description of the Related Art A technique for forming a fine pattern is important for high integration of LSI and realization of a device having a new function, and a method for forming a very fine structure with less damage is required. Current LS
In the manufacturing process of I, the resist pattern formed by various lithography methods is used as a mask to transfer the material to the workpiece by an etching method utilizing the assist effect of ions (for example, a reactive ion etching (RIE) method).

[0003]

However, such a pattern transfer method has the following problems. First,
When the reaction promoting effect by ion bombardment is used in the etching process, defects are introduced into the workpiece and the electrical and optical characteristics are degraded. Further, the resist pattern is required to have a certain thickness or more to withstand the etching process. Therefore, it becomes difficult to form an extremely fine pattern. Further, the resist is exposed to the air during the resist coating process, or the polymer constituting the resist contaminates the surface, so that the impurity concentration at the regrowth interface is high and cannot be put to practical use. Such a problem becomes more remarkable as the element becomes finer.

[0004] In order to solve these problems, an etching method using an electron beam without a resist coating step has been studied. Japanese Patent Application Laid-Open No. Hei 2-182530 discloses that, when oxygen and carbon adsorbed on the wafer surface in the atmosphere are irradiated with an electron beam in a vacuum, the irradiated portion of oxygen and carbon is stripped off and the wafer surface is exposed. ,
The invention describes that etching can be performed by contacting a reactive gas.

Japanese Patent Application Laid-Open No. Hei 3-11721 discloses G
When an aAs substrate is immersed in an organic solvent to adsorb carbon and oxygen on the surface, and irradiated with an electron beam while applying chlorine gas, the adsorbed layer in the irradiated portion is removed and the substrate in that portion is etched by chlorine. The invention has been described.

However, in these inventions, the mask layer on the surface is formed by adsorption in the air, and there is a problem in controllability and reproducibility. In addition, an oxide film must actually be formed on the surface, which adversely affects controllability and reproducibility.
In addition, carbon and oxygen are obviously contaminants, and there is a problem that the contaminants are used as a mask material and contaminate the substrate.

An object of the present invention is to provide a method and apparatus for forming a fine pattern which eliminate the above-mentioned problems.

[0008]

The present invention is characterized in that an inert treatment is performed by forming an adsorption layer on a clean surface of a workpiece in a vacuum, and this is used as a mask layer for subsequent etching. This is a method for forming a fine pattern.

For the etching, a method of irradiating an inert layer mask with an electron beam, stripping the adsorption layer in a desired area to form a pattern, and thereafter performing gas etching may be used.

After the gas etching, the inert layer can be removed again in a desired area in a vacuum to obtain a clean surface, and a new pattern can be formed or regrown.

When hydrogen or hydrogen sulfide is used as the adsorbing layer and supplied in the form of radicals, controllability and reproducibility are improved as compared with simple adsorption.

Further, as an apparatus for realizing the fine pattern forming method of the present invention, there are provided an inlet for supplying a gas for forming an adsorbing layer, a vacuum chamber for forming an adsorbing layer provided with a device for radicalizing the gas, and A vacuum chamber for electron beam irradiation provided with an electron gun, its deflection system and a precision moving mechanism for a workpiece, and a vacuum chamber for gas etching are used, and these chambers are connected by a vacuum transfer mechanism.

[0013]

FIG. 1 shows the concept of the present invention. Various processes such as substrate heating are performed on the workpiece 103 in an ultra-high vacuum to obtain a clean surface. This clean surface, for example, causes rearrangement in a semiconductor material such as silicon or gallium arsenide, but the substrate constituent atoms 102 are exposed, and basically dangling bonds 101 are present on the surface and are very active compared to the inside of the material. The gas etching proceeds when exposed to a reactive gas under certain conditions. In the present invention, by supplying specific molecules, atoms or radicals to such a clean surface, an inactive layer 104 is formed on the surface and used as a mask for preventing contact between a workpiece and a reactive gas. Here, in forming the inert layer, a gas that chemically bonds to the constituent atoms of the substrate on the surface of the workpiece and forms a stable adsorption layer may be introduced into the vacuum layer. In order to promote the above-described chemical bonding 105, it is effective to increase the temperature of the substrate, heat a gas to be supplied, or extract radicals from plasma. Further, when selecting the gas, consideration should be given to the resistance to the reactive gas used for gas etching. On the other hand, electron beam 1
This is performed using the effect of desorption of adsorbed atoms (electron impact desorption effect) accompanying the 06 irradiation. The electron impact desorption excites a surface reaction in an electron beam irradiation area to remove adsorbed substances, and the active surface 107 is exposed again. Accordingly, the mask layer can be patterned by irradiating the surface of the previously formed inactive layer with a focused electron beam and scanning it with a desired shape. In general, an electron beam not only can control a focused beam of a nanometer level with high precision through various lenses and deflection systems, but also can easily form a fine pattern because a surface layer to be removed is limited to an adsorption layer. Next, the substrate is set at a constant temperature, and a reactive gas 108 is supplied to perform gas etching. Here, in the region where the active surface of the workpiece is exposed by the electron beam, the reaction product 109 is desorbed by irradiation of the reactive gas and etching proceeds, whereas in the region where the inactive layer is inserted as a mask, As a result of the inhibition of the etching reaction, a fine pattern can be formed. Furthermore, for certain types of inactive layers, the reactive gas is exhausted after etching and then the substrate is heated,
This mask layer can be removed, and further processing can be performed starting from the clean surface that has reappeared as a starting point, and regrowth can be performed on the processed surface.

[0014]

FIG. 2 shows an example of the configuration of a test apparatus for carrying out the present invention. The apparatus includes a sample exchange chamber 201, a mask layer forming chamber 202, an electron beam irradiation chamber 203, and an etching chamber 204.
Consists of four rooms. Each includes a vacuum evacuation system 206, a sample exchange chamber 10 in the exhaust by the turbo molecular pump from the viewpoint of operability ^- is ⁷ Torr stand half ultimate vacuum. The mask layer forming chamber and the etching chamber are evacuated by a chemical-specific turbo molecular pump to introduce various gases into the vacuum layer.
It is on the order of ^0-10 Torr. The electron beam irradiation chamber is evacuated by the ion pump, the ultimate vacuum is 10 ^{- 1 0} Torr
It is a stand. Before introducing Si and GaAs as workpieces into the apparatus, various contaminations on the sample surface and natural oxide films were removed by various types of wet etching. After washing, it was quickly introduced into the sample exchange chamber and evacuated. After sufficiently exhausting the sample exchange chamber, the sample was transported to the mask forming chamber by the transfer rod. Then vacuum mask formation chamber using a heating mechanism with the sample stage 207 and the sputtering ion gun 213 10 ^- while keeping the ^{1 0} Torr stand, with damage recovery step by substrate heating or ion sputter cleaning and heating the substrate, the A clean surface of the workpiece was obtained. A mask layer forming gas 211 such as H ₂ or H ₂ S was supplied in a radical state to this surface through a radical generator 210 to form an inert adsorption layer having a thickness of several atomic layers on the outermost surface. After exhausting the gas, the sample is transferred to the electron beam irradiation chamber 203, and the electron gun 209 is used.
The focused electron beam was scanned onto the sample using the deflection system and the sample stage 208 with a precision moving mechanism to desorb the inert adsorption layer and pattern the mask layer. This was transported to the etching chamber 204, and after setting to a desired substrate temperature, an etching gas 212 was introduced to etch a region not covered by the inert mask layer, thereby transferring a fine pattern. When another etching is subsequently performed, the sample is heated in the mask layer forming chamber, the inert adsorption layer on the entire surface of the sample is thermally desorbed, and a clean surface of the workpiece is obtained again. And proceeded with the following process.

[0015]

According to the present invention, since a mask layer is formed in a vacuum, no oxide film is formed on the substrate surface, and controllability and reproducibility are improved. Further, since the mask layer is positively formed by supplying hydrogen, hydrogen sulfide, or the like in a radical state, controllability and reproducibility are superior to those in the case of simply adsorbing carbon or oxygen. In addition, since the adsorption layer can be desorbed by heating the substrate after the etching is completed, the substrate is not contaminated with hydrogen or hydrogen sulfide as compared with the case where the substrate is used as a carbon or oxygen mask, and has appeared again. Further processing and film formation can be performed starting from the clean surface. If the formation of the mask layer and its patterning, etching, removal of the mask, and subsequent processing and film formation are all performed by a vacuum integrated process, contamination at the interface during processing and film formation can be eliminated.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is a diagram showing an example of an experimental device for implementing the present invention.

[Explanation of symbols]

 101 Dangling Bond 102 Substrate Constituent Atom 103 Workpiece 104 Inactive Layer 105 Chemical Bonding 106 Electron Beam 107 Active Surface 108 Reaction Gas 109 Reaction Product 201 Sample Exchange Room 202 Mask Layer Forming Room 203 Electron Beam Irradiation Room 204 Etching Room 205 Transfer rod 206 Vacuum evacuation system 207 Sample table with heating mechanism 208 Sample stage with precision moving mechanism 209 Electron gun 210 Radical generator 211 Mask layer constituent gas 212 Etching gas

Claims (4)

(57) [Claims] Claims: 1. A constituent atom of a workpiece is exposed in a vacuum ,
Form a clean surface with dangling bonds on the surface
After that, the gas chemically bonded to the constituent atoms of the workpiece
The dangling bob on the outermost surface of the workpiece.
Atomic layer chemically bonded to the adsorption layer of the gas and the gas
A method for forming a fine pattern, characterized in that a gas is introduced only to form an inactive layer having a thickness of an appropriate thickness, an inactive treatment is performed, and the inactive layer is used as a mask layer for subsequent etching. 2. A fine pattern forming method according to claim 1, characterized in that the gas etching after patterning strip off the adsorption layer of the desired region by irradiating an electron beam to said inactive layer. 3. The method according to claim 2, wherein after the gas etching, the inactive layer in a desired region is removed again in a vacuum to obtain a clean surface, and subsequently, a new pattern is formed or regrown in a vacuum. Fine pattern forming method. 4. The method according to claim 1 , further comprising the step of applying the workpiece to a clean surface of the workpiece in a vacuum.
An inert adsorption layer with a thickness of several atomic layers is formed on the outermost surface of the structure
Irradiate only the mask constituent gas to form an adsorption layer.
Passivation process, which is used for subsequent etching.
A fine pattern forming method used as a mask layer for
, As the adsorption layer, the fine pattern forming method which comprises using a layer formed of hydrogen or hydrogen sulfide in a radical state is supplied to the clean surface of the workpiece.