JPH0697653B2 - Thin film fine pattern forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a fine pattern of a thin film in a semiconductor device manufacturing process.

[Conventional technology]

As the density of integrated circuits has increased, ultra-fine processing with a pattern width of several thousand Å has become necessary. For such ultra-fine processing, it is necessary to use exposure by electron beam, X-ray or ion beam. Polymethylmethacrylate (PMMA) used for electron beam exposure has the drawback of low sensitivity. It takes a long exposure time, and if it is made thick enough to have etching resistance when processing the base film, However, there was a problem in that the resolution degradation due to forward scattering and secondary electron scattering inevitably occurred. As one of the attempts to increase the sensitivity, methacrylate having fluoroalkyl in the side chain (J. Electrochem. Soc., Vol. 124, p. 1648 (1977)
Year)) as a resist material or a Langmuir-Blodgett film as a thin film resist (Thin Solid Films)
Vol. 99, pages 1-329 (1983)) have been proposed, but all of them have a problem that their dry etching resistance is weak. A three-layer resist consisting of resin, inorganic material, and resin is used to enhance dry etching resistance, but the thickness of the upper resin layer is such that it has an enching resistance when processing the lower inorganic material. However, the resolution deteriorates with the thickness. The most desirable processing method for forming an ultrafine pattern is to pattern an extremely thin resist using a low-energy electron beam and etch the lower thin film, or select a thin film based on the resist pattern. It is a method of forming the film. As a method of selectively forming a thin film, it is considered that a technique of selectively adhering the thin film due to the difference in surface material will be extremely effective.
Since the fluorine-based resin has a very low surface free energy, several attempts have been made to utilize this fluorine-based resin for selective attachment of substances. For example, a waterless lithographic printing method utilizing the water-repellent / oil-repellent fluorine-based photosensitive resin that repels ink (Daikin et al., JP-A-51-58105, 3M JP-B-55)
-27336), and a flattening wiring method in which a metal is embedded by selective vapor deposition using a fluorine-based resin film patterned by a photoresist film (Toshiba's Japanese Patent Publication No. 53-42396).

[Problems to be solved by the invention]

However, the lithographic printing method is a liquid phase deposition method, and is difficult to be applied to a field such as a semiconductor manufacturing process where strict requirements for fine dimensions and uniformity of film thickness are required.

On the other hand, in the flattening wiring method by the selective vapor deposition, since the fluororesin having the photosensitivity for heating and depositing the fluororesin up to about 200 ° C. cannot be used for the flattening, the fluororesin cannot be formed on the fluororesin film. Furthermore, it is necessary to apply a photoresist for patterning, and vapor deposition of metal atoms is a physical deposition phenomenon and does not involve a chemical reaction, so the difference in energy required for thin film formation depending on the surface material is small, and the fluorine resin film It is difficult to make use of the difference in surface material between the underlayer and the underlying film on which metal should be deposited, and selective deposition is limited to special metals such as gold, and an inorganic insulating film such as a metal compound is selectively deposited. It was difficult to use for fine processing.

[Means for solving problems]

FIG. 1 is a schematic process sectional view for explaining the constitution of the present invention. That is, according to the present invention, first, the first thin film 2 having extremely low surface free energy is patterned on the substrate 1. Next, CVD (Chemical Vapor Deposition) method
Of the thin film 2 of the first thin film 2 and the portion 27 of the first thin film 2 to which no adhering is applied by utilizing the difference in the adsorption energy of the reaction molecule with respect to the difference in the surface free energy of the thin film 2 It is characterized in that the second thin film 3 is grown intentionally.

That is, in the thin film fine pattern forming method of the present invention, the first thin film having a low surface free energy is exposed by irradiation of a photon beam or a particle beam, and then developed and patterned on the substrate, and the above-mentioned method is used by the CVD method. The method has a step of selectively growing an inorganic insulating film as a second thin film on a portion where the first thin film is not attached, and the first thin film is crosslinked or decomposed by irradiation of the photon beam or particle beam. A first resin or a mixed resin of a photosensitive resin and the first resin, and the first resin is a polymer containing at least a carbon atom and a hydrogen atom, and has a side chain with perfluoro. It is a resin having an alkyl.

Further, on the substrate on which the first thin film having a low surface free energy is patterned, the inorganic insulating film is selectively grown as the second thin film on the portion where the first thin film is not attached by the CVD method. The first thin film has a step of
A resin film containing at least carbon atoms, or after patterning a carbon film, carbon fluoride is formed on the surface by fluorinating the surface with heat or plasma, and the film has a low surface free energy. .

In addition, the first thin film having a low surface free energy is exposed by irradiation with a photon beam or a particle beam, and then developed and patterned on the substrate, where the first thin film is not attached by the CVD method. A step of selectively growing an inorganic insulating film as a second thin film, wherein the first thin film is a chain polymer having a perfluoroalkyl group at one end and a hydrophilic group at the other end. It is characterized in that it is a film in which an organic substance having a double or triple bond which can be polymerized by irradiation with the photon beam or particle beam is attached to the substrate in a monomolecular layer or several molecular layers.

Further, after the patterned first thin film is formed, a vapor phase metal compound having a property of being hydrolyzed by combining a halogen atom or an alkyl group with a metal is reacted with water vapor by the CVD method. The above-mentioned inorganic insulating film is selectively grown.

[Action]

A feature of the present invention is to selectively grow a thin film by using the CVD method depending on the difference in the surface free energy of the underlayer.
Therefore, it is necessary that the surface free energy of the first thin film patterned on the substrate is sufficiently lower than the surface free energy of the underlying layer to which the first thin film is not attached.

In order to explain this surface free energy, the critical surface tension corresponding to the surface free energy of typical substances is shown. The critical surface tension of perfluoroalkyl acrylate (PPFAA) CF ₃ (CF ₂ ) ₆ CH ₂ -A, which is a fluorine-based resin that is an example of a thin film having low surface free energy in the present invention, is 10.4 dyn / cm, Hydrocarbon, which is a typical organic substance used, is 31 dyn / cm, and chlorocarbon is 40 dyn / cm, while Si, SiO _{2 and the} like which are typical inorganic substances used for LSI manufacturing have a high surface. It has free energy and is over 100 dyn / cm. There is about this difference, that is, the difference in surface free energy level,
The present invention takes advantage of this difference. This difference in surface free energy affects the magnitude of activation energy when a thin film is deposited on the surface when reacting from the gas phase in the CVD method, and the film can be selectively formed.

FIG. 2 is a diagram showing an example of a CVD apparatus used for selective growth. 28 is a reaction chamber, 29 is a sample, 30, 31, 32 are N ₂ respectively.
A gas flow meter, 33 is a ring pipe, and SiCl ₄ and water vapor (H ₂ O) are introduced into the reaction chamber 28 with N ₂ as a carrier gas, and a thin film, in this case, a silicon oxide (SiO ₂ ) film is selected. Grow.

FIG. 3 is a diagram showing the deposition rate of a thin film and the gas flow rate dependence of the nucleation of the thin film. The horizontal axis represents the flow rate of the carrier gas N ₂ for transporting SiCl ₄ (the flow meter 31 in FIG. 2).
Flow rate). The flow rate of the carrier gas N ₂ for transporting H ₂ O (flow rate indicated by the flow meter 32) is 100 cc / min, and the flow rate of N ₂ as a diluent gas (flow rate indicated by the flow meter 30) is 2.
It is 5 l / min. The vertical axis on the left side shows the deposition rate on silicon (Å / min), and the vertical axis on the right side shows the area occupied by the nuclei of the deposited film on PPFAA / the area of PPFAA. In the figure, ○ indicates the deposition rate on silicon corresponding to the vertical axis on the left side, ■ and □ correspond to the vertical axis on the right side, ■ indicates when the film was deposited on the Si by 1000Å, and □ indicates the deposition on Si. The nuclear occupation area / PPFAA area on PPFAA when the film is deposited at 2000 Å is shown.

As shown in FIG. 3, as the flow rate of the reaction gas of SiCl ₄ is increased, nuclei of SiO ₂ are also generated on PPFAA and the selectivity of film deposition is deteriorated. On the other hand, when the flow rate of the reaction gas of SiCl ₄ is decreased (for example, the flow rate of N ₂ is 0 and the pressure of the SiCl ₄ reaction gas is only), the deposition rate is about 200 Å / min on Si. It can be seen that a condition that no deposition is obtained on the PPFAA film can be obtained. This is because when the flow rate of the reaction gas is reduced, the activation energy for forming the film increases, and the difference in the material of the surface greatly affects the deposition of the film.

In the selective growth of the present invention, as shown in FIG.
A thin film such as Si is not deposited at all on a thin film with low surface free energy such as FAA, and although it is not recognizable as a film, it is attached as an atom and a thing like a nucleus is formed on the surface. Such slight adhesion is
Is easily peeled off in the manufacturing process of
A selectivity of 1 or 1 can be achieved.

〔Example〕

Example 1 Examples of the fluorocarbon resin that is sensitive to electron beams include perfluoroalkyl acrylate (CF ₃ (CF ₂ ) _n (CH) -A) or perfluoroalkyl methacrylate (CF ₃ (CF ₂ ) _n CH _2-
M) (however, n3, A is an acrylate chain, and M is a methacrylate chain).

FIGS. 4A and 4B show an embodiment in which a silicon oxide thin film is selectively deposited using perfluoroalkyl acrylate. Perfluoroalkyl acrylate 2 is applied on the semiconductor substrate 1 to a predetermined thickness, and electron beam irradiation 19 is applied to a predetermined location (FIG. 4 (a)). The perfluoroalkyl acrylate that has been irradiated with the electron beam crosslinks, and if, for example, Freon 113 is used as the developing solution, only the part that has not been irradiated is selectively dissolved and removed (FIG. 4 (b)). Next, the sample is subjected to steam, S
When exposed to a mixed gas atmosphere of iCl _4, the gas molecules are selectively adsorbed and reacted with a high surface free energy where the perfluoroalkyl acrylate pattern 2 ′ is not attached and the same thickness as that of the film 2 ′. A silicon oxide film 3 is formed (FIG. 4 (c)). At this time, the partial pressures of steam and SiCl ₄ were 10 to 100 Torr, respectively. After that, the perfluoroalkyl acrylate film 2'is removed by using oxygen plasma or an organic solvent to obtain a desired thin film fine pattern.

When perfluoroalkyl methacrylate is used instead of perfluoroalkyl acrylate, it is decomposed by electron beam irradiation, so that the inverted pattern of the above embodiment is formed.

Further, in order to expose using ultraviolet rays instead of electron beams, as a resist proposed in lithographic printing, for example, a copolymer of perfluoroalkyl methacrylate and azide-containing methacrylate (Akayama Yamaoka et al., Japan Printing Society,
May 29, 1980 No. 13) etc. may be used.

Further, it is also possible to selectively grow other metal oxides such as aluminum oxide and molybdenum oxide, and to hydrolyze the metal compound gas (Al (CH ₃ ) ₃ , (Al (iC ₄ H ₉ ) ₃ , Mo).
(allyl) ₄ ) and steam may be used.

Example 2 FIGS. 5 (a) and 5 (b) show an example using a film having a low surface free energy at the molecular layer level.

An organic substance 4 having a double or triple bond in a chain polymer having a fluoroalkyl group at one end and a hydrophilic group at the other end is attached to the substrate 5 by a Langmuir-Blodgett method or adsorption from the gas phase to form a monolayer or A few molecular layers thick are attached (Fig. 5 (a)). Examples of this substance are CF ₃ (CF ₂ )
There is a molecule of ₆ (CH ₂ ) ₁₁ CCOOH (IBM US Pat. No. 4,169,904). This film 4 is irradiated with an electron beam 20 or ultraviolet rays to crosslink the predetermined parts (Fig. 5 (b)) and then developed with chloroform to pattern a thin film having a low surface free energy (Fig. 5 ( c)). Next, the inorganic insulating film 6 is selectively grown using the CVD method as shown in Example 1 (FIG. 5 (d)). Then, the organic material 4'is removed by using oxygen plasma or an organic solvent to obtain a desired thin film fine pattern.

Example 3 An example in which the method of Example 1 or 2 is applied to the formation of a thin film fine pattern using dry etching.
It shows in (e).

A film 8 is deposited on the semiconductor substrate 7, and a resin film 9 is applied on the film 8 (FIG. 6A). The film 8 may be any film used for semiconductor devices such as Al, Si, and SiO ₂ . As the resin film 9, it is desirable to use an organic film having selectivity with the underlying film 8 to be dry-etched, such as various photoresists and polyimides. The film thickness depends on the thickness of the film 8 to be processed, but is about 5000Å to 1 μm. desirable. Next, the film 10 having a fluoroalkyl group used in Example 1 or Example 2 is deposited and patterned in the same manner as in Examples 1 and 2 (FIG. 6 (b)). The thickness of the film having a fluoroalkyl group may be extremely thin, from the monomolecular layer to about 1000 Å or less. Next, in the same manner as in Example 1, the inorganic insulating film
11 is selectively deposited on the unattached portion of the film 10 having a fluoroalkyl group (FIG. 6 (c)). Next, the resin film 9 is processed by reactive ion etching of oxygen using the pattern of the inorganic insulating film 11 as a mask (FIG. 6 (d)). At this time, the film 10 is also removed. Then, using the resin film 9 as a mask, the film 8 is processed by reactive ion etching using an optimum etching gas (FIG. 6 (e)). At this time, if the film 11 and the film 8 are the same material, the film 11 is removed by the etching, but if they are different materials, the film 11 is removed before the etching. Then, the resin film 9 is removed using oxygen plasma or an organic solvent to obtain a desired thin film fine pattern.

Example 4 After forming a film pattern 13 having a fluoroalkyl group on the substrate 12 by the method of Example 1 or Example 2 (FIG. 7 (a)), an organic metal gas such as Al (CH ₃ ) ₃ , By irradiating with an ultraviolet ray in an atmosphere of about 10 Torr, the Al film 14 is selectively formed only on the part where the film 13 having a fluoroalkyl group is not attached.
Is deposited by the CVD method (FIG. 7 (b)). After this, membrane 1
3 is removed to obtain the desired metal film pattern. As another organometallic gas, for example, Cd (CH ₃ ) ₂ , Zn (CH ₃ ) ₂ or the like is used, and Cd, Z
It can be applied to the deposition of other metals such as n.

Fifth Embodiment Using the thin film (for example, a silicon oxide film) 15 selectively formed on the silicon substrate 21 by the method of the first or second embodiment as a mask, the silicon substrate 21 is etched under the conditions that are usually performed (see FIG. )), And ion implantation (FIG. 8 (b)) can be performed.

Example 6 A patterned resin film or carbon film 24 is formed on a substrate 23 (FIG. 9 (a)), and then the surface of the patterned thin film 24 is fluorinated in a plasma containing fluorine to reduce the surface free energy. The surface 25 is formed (FIG. 9 (b)). next,
In the same manner as in Example 1, CVD is performed on the portion without the patterned thin film 24.
A predetermined film 26 is selectively grown by the method (FIG. 9 (c)). After that, the surface 25 and the pattern thin film 24 are removed by oxygen plasma to obtain a desired thin film pattern (FIG. 9 (d)).

〔The invention's effect〕

As described above, according to the present invention, various thin films such as metal and inorganic insulating films can be selectively grown by utilizing the difference in surface free energy of the underlying material. Further, since the thin film having a low surface free energy may have a single molecular layer, it is possible to form an ultrafine pattern.
(The width is 1000Å in the method of the first embodiment, and is several in the method of the second embodiment.
Can form patterns up to 100Å. Further, since pattern formation can be performed without using dry etching (Examples 1, 2, 4, 5), there is an advantage that deterioration of the element due to ion bombardment of dry etching can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic process sectional view for explaining the constitution of the present invention, FIG. 2 is a view showing an example of a CVD apparatus used for selective growth, and FIG. 3 is a deposition rate of a thin film and a gas for nucleating the thin film. FIG. 4 (a) to FIG. 4 (c) are process cross-sectional views showing the first embodiment of the present invention, and FIG. 5 (a) to FIG.
(D) is a process sectional view showing a second embodiment of the present invention,
FIGS. 7A to 7E are process sectional views showing the third embodiment of the present invention, and FIGS. 7A and 7B are process sectional views showing the fourth embodiment of the present invention. 5A and 5B show the fifth embodiment of the present invention.
9A to 9D are process sectional views showing a sixth embodiment of the present invention. 1, 5, 7, 12, 21, 21, 22, 23 ... Substrate 2, 2 '... Perfluoroalkyl acrylate film 3, 15, 17 ... Silicon oxide film 4, 4' ... CF ₃ (CF ₂ ) ₆ (CH ₂ ) ₁₁ C CCOOH film 6, 11 …… Inorganic insulation film 8 …… Thin film to be processed 9 …… Resin film 10,13 …… Resin film having perfluoroalkyl group 14 …… Al film 16 …… … Groove 18 …… Implanted region 19,20 …… Electron beam 24 …… Resin or carbon film 25 …… Surface with low surface free energy 26 …… Patterned thin film 27 …… No thin film adhered Part 28 …… Reaction chamber 29 …… Samples 30, 31, 32 …… Flowmeter 33 …… Ring pipe

Claims (6)

[Claims] 1. A first thin film having a low surface free energy,
An inorganic insulating film is selectively used as a second thin film on a portion of the substrate which has been developed and patterned after being exposed by irradiation with a photon beam or a particle beam, by a CVD method, at a portion where the first thin film is not attached as a second thin film. A step of growing the first thin film, the first thin film is made of a first resin that is crosslinked or decomposed by irradiation of the photon beam or particle beam, or a mixed resin of a photosensitive resin and the first resin, and The method for forming a thin film fine pattern, wherein the first resin is a resin having a polymer containing at least carbon atoms and hydrogen atoms and having perfluoroalkyl in a side chain. 2. A vapor phase metal compound having a property of being hydrolyzed by forming a bond between a halogen atom or an alkyl group and a metal after forming the patterned first thin film, and water vapor. The method for forming a thin film fine pattern according to claim 1, wherein the inorganic insulating film is selectively grown by reacting by a method. 3. An inorganic insulating film as a second thin film is selectively formed on a portion of the substrate, on which the first thin film having a low surface free energy is patterned, by a CVD method at a portion where the first thin film is not attached. A step of growing a film, wherein the first thin film forms a carbon fluoride film on the surface by patterning a resin film containing at least carbon atoms or a carbon film and then fluorinating the surface with heat or plasma. Is
A thin film fine pattern forming method characterized in that the film has a low surface free energy. 4. After the formation of the patterned first thin film, a vapor phase metal compound having a property of being hydrolyzed by combining a halogen atom or an alkyl group with a metal, and steam are used for the CVD. 4. The thin film fine pattern forming method according to claim 3, wherein the inorganic insulating film is selectively grown by reacting by a method. 5. A first thin film having a low surface free energy,
An inorganic insulating film is selectively used as a second thin film on a portion of the substrate which has been developed and patterned after being exposed by irradiation with a photon beam or a particle beam, by a CVD method, at a portion where the first thin film is not attached as a second thin film. The first thin film having a perfluoroalkyl group at one end and a hydrophilic group at the other end can be polymerized by irradiation with the photon beam or particle beam. A method for forming a fine pattern of a thin film, which is a film in which an organic substance having a double or triple bond is attached on the above substrate in a monomolecular layer or several molecular layers. 6. A vapor phase metal compound having a property of being hydrolyzed by forming a bond between a halogen atom or an alkyl group and a metal after forming the patterned first thin film, and water vapor as the CVD. The thin film fine pattern forming method according to claim 5, wherein the inorganic insulating film is selectively grown by reacting by a method.