JP3952455B2 - Nano-patterning method using organic monomolecular film as resist - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for performing nanoscale patterning on a layer to be patterned such as a silicon oxide film formed on a silicon substrate, and more specifically, by using an organic monomolecular film as a resist, The present invention relates to a nano-patterning method that enables easy patterning.
[0002]
[Prior art]
Forming a fine metal pattern on the surface of a semiconductor substrate is an important process in manufacturing semiconductor devices, microelectromechanical systems (MEMS), and the like. In order to realize this process, a photoresist layer is currently formed on a layer to be patterned such as a conductor layer or an insulating layer for embedding a conductor layer, and a short wavelength is passed through a mask having a predetermined pattern on this photoresist layer. A resist pattern is formed by irradiating light and removing the alkali-soluble portion after irradiation with an alkali developer, and the target layer to be patterned is etched using this resist pattern as a mask.
[0003]
In such a patterning method using a resist pattern, further miniaturization has always been demanded. Recently, by improving an exposure apparatus and developing a new composition of a photoresist composition, several hundred nanometer order has been developed. Patterning is becoming possible. However, when the goal is to achieve patterning on the order of several tens of nanometers, photoresist materials have physical limitations in reducing the coating thickness, causing short-wavelength light to spread due to the thickness, and resist materials Has a molecular weight distribution, the resolution of the resist deteriorates along with the molecular weight distribution, it is difficult to stabilize the sensitivity of the photoresist to short-wavelength light, and the photoresist is irradiated with short-wavelength light There are many problems caused by the resist material itself, such as the fact that back reflection is likely to occur and the resolution is likely to deteriorate due to the reflected light, and further miniaturization of patterning using photoresist is difficult. It is considered.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and it is an object to provide a nano patterning method capable of easily realizing fine patterning on the order of several tens of nanometers with high resolution. To do.
[0005]
[Means for Solving the Problems]
For many years, the present inventors have been studying whether a film having a thickness as thin as possible can be formed on the surface of an inorganic material such as a semiconductor. Recently, the following findings have been obtained.
[0006]
That is, “When an inorganic oxide film is exposed to a solution or vapor of an organic molecule having a terminal functional group having an affinity for the inorganic oxide film, the organic molecule reacts with the surface of the inorganic oxide film by a chemical reaction such as a covalent bond or an ionic bond. The organic molecules are densely assembled on the surface of the inorganic oxide film due to the interaction between the organic molecules, and a monomolecular film is formed in which only one molecule is densely gathered in the thickness direction and molecules are densely gathered in the width direction. I came to know that. By irradiating a controlled electron beam locally on the monomolecular film, it can be detached from the surface of the inorganic oxide film one molecule at a time. Further, when an organic silane compound is used as the organic molecular material, the obtained monomolecular film has resistance to a conventional etching solution and etching gas, that is, can be used as a resist film. When an organic silane compound is used as the monomolecular film forming material, the target inorganic oxide film is silicon oxide, glass, alumina, etc., and the organic silane is formed on these surfaces by gas phase chemical reaction or liquid phase reaction. A monomolecular film made of molecules can be formed. Based on such technology, the present inventors have succeeded in forming a small area groove in a silicon oxide film formed on a silicon substrate and embedding nickel by electroless nickel deposition in this groove. (Non-Patent Document 1).
[0007]
[Non-Patent Document 1]
Daisuke Niwa and two others (Daisuke Niwa et al.), “Fabrication of Ni Nanostructure on Silicon Wafer by Electroless Deposition”, June 22, 2001, 60th Semiconductor Integrated Circuit Technology Symposium [0008]
The inventors of the present invention have performed unique patterning in the micro nickel embedding technique. However, the present inventors have conducted further experiments and examinations on whether or not this technique can be extended to general micro patterning. It was also found that a nano-scale patterning method that is difficult to achieve with current photoresist patterning can be easily provided.
[0009]
The present invention has been made on the basis of such findings, and a nanopatterning method using an organic monomolecular film as a resist according to the present invention, as shown in FIG.
(A) a monomolecular film forming step of forming the organic monomolecular film 3 on the surface of the layer to be patterned 2;
(B) a patterning step of removing a part of the organic monomolecular film 3 according to a predetermined nanoscale pattern by electron beam lithography and introducing an amount of gas that promotes detachment of the organic monomolecule into the patterning atmosphere ;
(C) an etching process in which the patterned layer 2 exposed in the removal portion 3a of the organic monomolecular film 3 is wet-etched using a hydrofluoric acid solution to form a pattern groove 4;
(D) immersing the patterned layer 2 having the pattern groove 4 in a nickel bath to form a micro nickel film on a silicon substrate;
It is characterized by having.
[0010]
Note that reference numeral 1 in FIG. 1 denotes a substrate that holds the patterning layer 2. For example, the substrate 1 is a silicon substrate, and the patterned layer 2 is a silicon oxide film.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the nano-patterning method using an organic monomolecular film as a resist according to the present invention having the above-described configuration, the organic monomolecular film is formed on the patterning layer using a self-organization process of the organic monomolecule. To do.
[0012]
As used herein, “self-organization” refers to the above-mentioned “when an inorganic oxide film is exposed to a solution or vapor of an organic molecule having a terminal functional group having an affinity for the inorganic oxide film, the organic molecule is formed on the inorganic oxide film. It binds to the surface by a chemical reaction such as covalent bond or ionic bond, and organic molecules are densely assembled on the surface of the inorganic oxide film due to the interaction between the organic molecules. In the process of forming a monomolecular film, “a densely assembled monomolecular film is formed.” In the process of forming a monomolecular film, “the organic molecules are densely assembled in the width direction of the surface of the inorganic oxide film due to the interaction between the organic molecules, and in the thickness direction. Means the phenomenon of “only one molecule”.
[0013]
This organic monomolecular self-assembly process can be developed by bringing the layer to be patterned into contact with a gas or solution containing an organosilane compound.
[0014]
In the case where a silicon layer is used as the layer to be patterned, the self-organization process of the organic monomolecule is expressed by immersing the silicon layer in an organosilane compound solution, and the organic monomolecule is converted into the silicon The organic monomolecular film is formed on the silicon layer by continuously arranging and bonding along the surface of the layer.
[0015]
Further, when a silicon oxide layer is used as the layer to be patterned, the self-organization process of the organic monomolecule is expressed by exposing the silicon oxide layer to the vapor of an organosilane compound, and the organic monomolecule is expressed. The organic monomolecular film is formed on the silicon oxide layer by arranging and bonding continuously on the surface of the silicon oxide layer along the surface.
[0016]
In the present invention, the organosilane compound is preferably an organoalkoxysilane.
[0017]
Further, in the present invention, in the patterning step (b) of removing a part of the organic monomolecular film according to a predetermined nanoscale pattern by electron beam lithography, the organic monomolecular film is disposed at and near the irradiation position of the electron beam. A trace gas that promotes separation may be introduced. As such a gas, oxygen gas is suitable.
[0018]
Etching in the step (c) of the present invention, that is, the etching step (c) for removing the layer to be patterned exposed in the removed portion of the organic monomolecular film is wet etching using a hydrofluoric acid solution, The organic monomolecular film is removed by dry etching using oxygen gas plasma ashing.
[0019]
Hereinafter, the configuration of the present invention will be described more specifically.
[0020]
Monomolecular film formation step (a)
The formation of the monomolecular film on the surface of the layer to be patterned is described in H.264. It can be carried out by a gas phase reaction or by a liquid phase reaction according to the method of Sugimura et al. (Langmuir, 16, 885, 2000). In the film formation by a gas phase reaction on the silicon oxide film, an organic silane monomolecular film can be formed by using organic alkoxysilane as a raw material and heating and vapor-depositing. The heating conditions may be appropriately selected in consideration of the boiling point, melting point, etc. of the raw material organoalkoxysilane. As an example, the heating temperature is preferably about 110 ° C., and the film formation time is preferably 3 hours or more.
[0021]
The organoalkoxysilane is preferably a trialkoxysilane in terms of adhesion and the like, and the alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms, particularly a methoxy group or an ethoxy group. The organoalkoxysilane includes an organoalkoxysilane corresponding to the organosilane described as constituting the monomolecular film.
[0022]
Specific examples of the organic alkoxysilane include CH ₃ (CH ₂ ) ₁₇ Si (OCH ₃ ) ₃ [97%, manufactured by Chisso Corporation], CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ [97%, manufactured by Chisso Corporation].
[0023]
Patterning process by electron beam lithography (b)
The monomolecular film can be removed in a predetermined pattern using electron beam lithography. The exposure conditions for electron beam lithography are preferably an acceleration voltage of about 25 kV and a dose of 300 to 500 μC / cm ² .
[0024]
Etching process (c)
The layer to be patterned exposed at the removal portion of the monomolecular film can be removed by etching using a hydrofluoric acid solution. The patterned monomolecular film can be removed by ashing using O ₂ plasma.
[0025]
The monomolecular film is not particularly limited as long as it is an organic molecular monomolecular film that is densely assembled by interaction between organic molecules and formed by self-organization, but an organic molecular monomolecular film made of organosilane is preferable. .
[0026]
As described above, the monomolecular film formed by self-organization has a uniform alignment of organic molecules formed by densely gathering organic molecules such as organosilane by the interaction between the organic molecules. A monomolecular film. When a patterning layer made of a specific material such as an inorganic oxide film is exposed to a solution or vapor of an organic molecule having a terminal functional group having an affinity for the patterning layer material, the organic molecule is exposed on the surface of the patterning layer. A monomolecular film of the organic molecules is formed at the solid / liquid or solid / gas interface.
[0027]
The organic silane may be either a functional organic silane or a non-functional organic silane, and is preferably a non-functional organic silane. The functional organic silane refers to an organic silane having a reactive substituent, and the non-functional organic silane refers to an organic silane having no reactive substituent.
[0028]
Preferable examples of the non-functional organosilane include linear alkyl silane and / or linear fluorinated alkyl silane, and in particular, linear alkyl silane having 8 to 20 carbon atoms and / or straight chain. More preferred are chain fluorinated alkylsilanes.
[0029]
Preferred examples of the linear alkylsilane include octadecyltrimethoxysilane, and preferred examples of the linear fluorinated alkylsilane include 5,5,5,4,4-pentafluorodecyltriethoxysilane. Can be mentioned.
[0030]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, a following example is only the illustration for describing this invention suitably, and does not limit this invention at all. The steps of the embodiment will be described with reference to FIGS. 1 (a) to 1 (c).
[0031]
Example 1
A silicon wafer was used as the film-forming substrate 1 for the self-organized organosilane monomolecular film, and a silicon oxide film having a thickness of 20 nm was formed as a patterning layer 2 on the surface by dry oxidation at 950 ° C. The substrate was washed with a mixed solution of sulfuric acid and hydrogen peroxide (sulfuric acid: hydrogen peroxide = 4: 1) at 120 ° C. for 10 minutes, then with a hydrofluoric acid solution, and finally with ultrapure water. . Next, after drying with dry nitrogen, an organic silane monomolecular film was formed on the silicon oxide film 2 as the monomolecular film 3.
[0032]
As organosilane molecules, alkylsilane: CH ₃ (CH ₂ ) ₁₇ Si (OCH ₃ ) ₃ (hereinafter referred to as ODMS), fluorinated alkyl silane: CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ (hereinafter referred to as FAS). For both ODMS and FAS, the substrate is sealed in a 20 cm ³ Teflon (registered trademark) container containing 0.2 ml of reagent, and 110 ° C. for 3 to 5 hours or more in an atmosphere with a dew point of −80 ° C. A gas phase chemical reaction was performed.
[0033]
As shown in the X-ray photoelectron spectroscopy spectrum of FIG. 2 and the chemical bonding state analysis described below, it was confirmed that the formed organic silane monomolecular film 3 was formed of molecules at a monomolecular level. It was also confirmed that the coverage was almost 100%. The film thickness was very thin such as ODMS: 2.6 nm and FAS: 1.7 nm.
[0034]
《Chemical bonding state analysis》
(X-ray photoelectron spectroscopy (XPS))
FAS
CF ₃ — (CF ₂ ) ₇ —CH ₂ —CH ₂ —Si—O—
1: 7: 1: 1
Measurement result = 1: 7.10: 1.03: 1.03
F / C ratio = 1.7
Measurement result: F / C = 1.69
[0035]
Patterning of self-assembled organosilane monolayer 3 The FAS monolayer 3 was patterned using electron beam lithography. The exposure conditions for electron beam lithography were AC voltage: about 25 V, current: about 50 pA, dose: about 400 μC / m ^2, and a dot pattern having 50 nm removal portions 3a at 200 nm intervals was produced.
[0036]
Etching of Silicon Oxide Film The silicon oxide film layer exposed in the removal portion 3a of the FAS monomolecular film 3 was removed by etching using a 1 wt% hydrofluoric acid solution for 90 seconds to form a pattern groove 4.
[0037]
The patterning pattern this time was a pattern in which a large number of pattern grooves 4 were arranged in a grid pattern as shown in the substrate plan view of FIG.
[0038]
Thereafter, in order to facilitate observation of the pattern shown in FIG. 3 using a scanning electron microscope, the silicon substrate 1 was wet etched using the patterned silicon oxide film 2 as a mask. As an etching solution, a solution of NH ₄ F: H ₂ O ₂ : H ₂ O = 10: 5: 100 was used. The etching selectivity of (silicon: silicon oxide) of this etching solution was 20: 1 or more. The silicon substrate 1 was subjected to pattern etching by being immersed in this etching solution for 10 minutes. As a result, it was confirmed that all the pattern grooves 4 were formed with high resolution. Moreover, by etching the silicon substrate, the pattern groove still maintains a high resolution of several tens of nanometers even though the pattern transfer is in two stages.
[0039]
Further, in this embodiment, in addition to the confirmation by the two-step etching, in order to confirm that the actual pattern is transferred and the silicon substrate is exposed, the pattern groove 4 is directly provided as follows. In particular, nickel was deposited by electroless deposition.
[0040]
Formation of Micro Nickel Film by Electroless Deposition The silicon substrate 1 after patterning is washed according to the method of Kern et al. (W. Kern et al., RCA Rev. 31, p187, 1970) and 1.5 × 10 ^{6 to} 2.0 × After washing with distilled water having a resistance of 10 ⁶ Ωcm, a pretreatment with hydrochloric acid overwater was performed. The silicon substrate 1 was immersed in an alkaline aqueous solution of pH 8.8 containing 0.1 M nickel sulfate and 0.3 M ammonium sulfate at 80 ° C. for 1 minute, and then immersed in a commercially available nickel bath to form a fine nickel film.
[0041]
As a result, it was confirmed that a nickel film was selectively formed in all the pattern grooves 4 and that nanopatterning was reliably realized.
[0042]
(Example 2)
In Example 1, the monomolecular layer was formed by the vapor phase method. However, in Example 2, the silicon substrate was immersed in an organosilane solution to cause a Grignard reaction, whereby an organic silicon monolayer was formed on the silicon substrate. A molecular layer was formed. As a result, an organic silicon monomolecular layer having the same film thickness as in Example 1 was formed.
[0043]
When this organic silicon monolayer was patterned by irradiating a controlled electron beam, a small amount of oxygen gas was introduced into the patterning environment. As a result, desorption of the molecule at the target position could be promoted.
[0044]
Whether the pattern groove is formed with sufficient resolution was confirmed by surface analysis of the pattern surface and selective deposition of copper in the groove using a hydrogen fluoride bath. The resolution of several tens of nanometers was confirmed.
[0045]
【The invention's effect】
As described above, the nano-patterning method according to the present invention includes:
(A) a monomolecular film forming step of forming an organic monomolecular film on the surface of the patterning layer;
(B) a patterning step of removing a part of the organic monomolecular film according to a predetermined nanoscale pattern by electron beam lithography;
(C) an etching step of removing the layer to be patterned exposed in the removed portion of the organic monomolecular film;
The organic monomolecular film can be easily formed using a self-assembly process of the organic monomolecule.
[0046]
Therefore, according to the nano-patterning method of the present invention, since the formed organic monolayer has a thickness of about 10 to 30 mm, unlike conventional polymer resists, the spread of short wavelength light due to the thickness, molecular weight There are significant advantages such as no degradation of resolution due to distribution, instability of sensitivity, and no influence of backscattering of exposure light. It becomes.
[Brief description of the drawings]
FIGS. 1A to 1C are process diagrams illustrating a nanopatterning method according to the present invention.
2 is a diagram showing an X-ray photoelectron spectrum showing analysis of an organic silane monomolecular film formed in Example 1. FIG.
3 is a plan view of a layer to be patterned that is patterned in Example 1. FIG.
[Explanation of symbols]
1 Substrate (silicon substrate)
2 Patterned layer (silicon oxide film)
3 Monomolecular film (organosilane monomolecular film)
3a Removal part 4 Pattern groove

Claims (8)

(A) a monomolecular film forming step of forming an organic monomolecular film on the surface of the patterning layer;
(B) a patterning step of removing a portion of the organic monomolecular film according to a predetermined nanoscale pattern by electron beam lithography and introducing an amount of gas that promotes the detachment of the organic monomolecule into the patterning atmosphere ;
(C) an etching process in which the patterned layer exposed in the removed portion of the organic monomolecular film is wet-etched using a hydrofluoric acid solution to form a pattern groove;
(D) immersing the patterned layer having the pattern groove in a nickel bath to form a micro nickel film on the silicon substrate;
A nano-patterning method using an organic monomolecular film as a resist characterized by comprising:   2. The nano-patterning method according to claim 1, wherein the organic monomolecular film is formed on the patterning layer using a self-assembly process of the organic monomolecule.   3. The nano-patterning method according to claim 2, wherein the self-assembly process of the organic monomolecule is expressed by bringing the layer to be patterned into contact with a gas or a solution containing an organosilane compound.   The layer to be patterned is a silicon layer, and the self-organization process of the organic monomolecule is expressed by immersing the silicon layer in an organosilane compound solution, and the organic monomolecule is formed on the surface of the silicon layer. The nano-patterning method according to claim 3, wherein the organic monomolecular film is formed on the silicon layer by continuously arranging and bonding along the surface.   The layer to be patterned is a silicon oxide layer, and the self-organization process of the organic monomolecule is expressed by exposing the silicon oxide layer to vapor of an organosilane compound, and the organic monomolecule is expressed by the silicon oxide layer. 4. The nano-patterning method according to claim 3, wherein the organic monomolecular film is formed on the silicon oxide layer by continuously arranging and bonding along the surface of the silicon oxide layer.   The nano-patterning method according to claim 3, wherein the organosilane compound is an organoalkoxysilane. The nanopatterning method according to claim 1 , wherein the gas is oxygen gas.   The organic monomolecular film is removed by dry etching using oxygen gas plasma ashing after the etching step (c) for removing the layer to be patterned exposed at the removal portion of the organic monomolecular film. Item 8. The nanopatterning method according to any one of Items 1 to 7.

Images