JP2004221414A - Method for building minute wiring structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a homogenous diffusion preventing film on the surface of a porous insulating film for building a minute wiring structure. <P>SOLUTION: A thin film such as a monomolecular film 4 is formed on the surface of a porous insulating film 2, and, thereon, a diffusion preventing film 8 and a conductive film 9 for wiring are formed successively. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a fine wiring structure, and more particularly, to preventing unevenness in the thickness of a barrier metal film due to holes when a low dielectric constant porous insulating film is used as an interlayer insulating film. And a method of forming a fine wiring structure having a characteristic for the structure.
[0002]
[Prior art]
The performance of wiring used in highly integrated semiconductor integrated circuit devices is determined by miniaturization, lowering of the dielectric constant and lowering of specific resistance of an interlayer insulating film. For example, it is required to realize a wiring forming process having a small thickness, for example, 70 nm.
[0003]
On the other hand, in order to improve the performance by lowering the dielectric constant of the interlayer insulating film, it is possible to lower the dielectric constant by making the interlayer insulating film porous (for example, see Patent Document 1).
[0004]
In order to improve the performance by lowering the resistance, copper (1.55 μΩcm at 0 ° C.) having a lower specific resistance has come to be used as a wiring material instead of aluminum (2.5 μΩcm at 0 ° C.) which has been conventionally used.
[0005]
However, since copper easily diffuses into an interlayer insulating film or a silicon substrate, it is necessary to form a diffusion preventing film. As the diffusion preventing film, generally, a high melting point metal such as Ta or a metal such as TaN or WN is used. Compounds have been used, which exhibit resistance values that are nearly 100 times higher than copper.
[0006]
Therefore, if the thickness of the diffusion prevention film is not made as thin as possible, the wiring resistance increases and the wiring performance deteriorates. This situation will be described with reference to FIG.
FIG. 8 shows the dependence of the wiring specific resistance on the wiring width when the Cu buried wiring is formed by the damascene method using the diffusion prevention film thickness as a parameter. The wiring width dependence of the resistance increases.
Here, Ta is assumed as the diffusion prevention film.
[0007]
Considering the specific resistance of 2 μΩcm or less at a wiring width of 70 nm, which is a required performance in recent years, it is necessary to reduce the thickness of the diffusion prevention film to 5 nm or less as is apparent from FIG.
[0008]
In order to uniformly form such a diffusion preventing film having a thickness of 5 nm or less according to the shape of wiring or via, instead of the conventional thin film forming method by sputtering, diffusion by chemical vapor synthesis (CVD) is used. The formation of the prevention film is performed.
[0009]
[Patent Document 1]
JP 2001-223269 A
[Problems to be solved by the invention]
However, when a porous insulating film is used as an interlayer insulating film when forming a diffusion barrier film by a chemical vapor synthesis method, the gas used for forming a thin film by the chemical vapor synthesis method is more likely to be used than the pores of the porous insulating film. Due to the small size of the molecules, gas enters the porous insulating film, making it impossible to form a uniform thin diffusion prevention film, and there is a problem that copper diffuses through a thin portion of the diffusion prevention film. Will be described with reference to FIG.
[0011]
9A and 9B, for example, when a Ta film 42 is formed by CVD on the entire surface of a porous insulating film 41 formed by applying methyl silsesquioxane (MSQ: Methyl Silsesquioxane), a hole 43 is formed. The thickness of the Ta film 42 is increased in the portion where the hole 43 is exposed, and the thickness of the Ta film 42 is reduced in the portion where the hole 43 is not exposed. Become.
[0012]
Conversely, if the thickness of the anti-diffusion film is increased in order to surely prevent the diffusion, the specific resistance of the wiring as a whole increases as described above, and the required performance for the wiring cannot be satisfied.
[0013]
Therefore, an object of the present invention is to form a uniform diffusion preventing film on the surface of a porous insulating film.
[0014]
[Means for Solving the Problems]
FIG. 1 is a diagram showing the basic configuration of the present invention, and means for solving the problems in the present invention will be described with reference to FIG.
In order to achieve the above object, the present invention relates to a method for forming a fine wiring structure, comprising the steps of uniformly forming a thin film on the surface of a porous insulating film 2; A step of sequentially forming the conductive film 9.
[0015]
As described above, by covering the hole 3 exposed on the surface of the porous insulating film 2 with the uniformly formed thin film, the film forming gas can enter the hole 3 when the diffusion preventing film 8 is formed. In addition, it is possible to form the diffusion prevention film 8 having a uniform film thickness, thereby forming the fine wiring 7 having a small specific resistance.
[0016]
In this case, after the thin film is formed as a uniform monomolecular film 4 on the solution surface, at least the porous insulating film 2 is immersed in the solution to form the monomolecular film 4 uniformly on the surface of the porous insulating film 2. That is, it is preferable to adhere using the LB (Langmuir-Blogett) method.
[0017]
As the monomolecular film 4, a monomolecular film composed of a combination of a hydrophilic group 6 and a hydrophobic group 5, particularly a monomolecular film in which the hydrophobic group 5 is a compound of silicon, oxygen, carbon, fluorine and nitrogen, for example, A monomolecular film in which the hydrophobic group 5 is composed of phthalocyanine and the hydrophilic group 6 is composed of butyl group is preferable.
In this case, the size of the hydrophobic group 5 may be any size as long as the diameter in the long axis direction is larger than the pore diameter of the porous insulating film 2.
[0018]
When the monomolecular film 4 is adhered to the porous insulating film 2, the X-type accumulation in which the monomolecular film 4 is transferred only at the time of descent when the substrate 1 is immersed, or both at the time of descent and at the time of pulling up Desirably, Y-type accumulation in which the monomolecular film 4 is transferred is performed, whereby the hydrophobic group 5 constituting the monomolecular film 4 can be attached to the porous insulating film 2 side.
In the case of the Z-type accumulation in which the monomolecular film 4 is transferred only when the substrate 1 is immersed and then pulled up, the hydrophilic group 6 is on the side of the porous insulating film 2 and the hole 3 cannot be closed.
[0019]
By providing the wiring 7 composed of the diffusion preventing film 8 and the conductive film 9 for wiring through such a monomolecular film 4, the reliability of the electronic device provided with the fine wiring structure can be improved.
[0020]
Although the thin film in the present invention is typically an insulating film, it may be a conductive film using a conductive organic material, and the porous insulating film 2 is typically an interlayer insulating film. However, the present invention is not necessarily limited to the interlayer insulating film.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Here, with reference to FIG. 2 and FIG. 3, the manufacturing process of the fine wiring structure according to the first embodiment of the present invention will be described.
Referring to FIG. 2A, first, a coating solution in which porogen is dispersed in a solvent of methyl silsesquioxane (MSQ) serving as a matrix is spin-coated on a silicon substrate 11 via a base insulating film 12, and then 300 to 450 The porous insulating film 13 is formed by annealing at ℃ and removing the solvent and curing.
In this annealing step, porogen evaporates or reacts with the matrix to form a hole 14 having a hole diameter of, for example, 20 °.
It should be noted that porogen does not indicate a specific substance, but uses various materials from various companies.
[0022]
Next, referring to FIG. 2B, a groove 15 for forming a wiring is formed using a normal photoresist method and an etching method.
[0023]
Next, as a molecule having a hydrophobic group 24 and a hydrophilic group 25 and a size of the hydrophobic group 24 larger than 20 angstroms, for example, a compound of phthalocyanine (Pc) and a butyl group (butyl) (t _-Butyl) After the 4 _H 2 Pc is dissolved by a solvent, was dropped on the pure water 21, to form a uniform monomolecular film 23 on the surface of the pure water 21.
[0024]
Next, as shown in FIG. 3D, the silicon substrate 11 on which the wiring grooves 15 are formed is immersed in pure water 21 so as to be perpendicular to the water surface 22.
[0025]
4 (e) and 4 (f). At this time, by using the X-type accumulation in which the monomolecular film 23 is transferred only when the silicon substrate 11 is lowered in the dipping step, when the silicon substrate 11 is pulled up, the inner surface of the groove 15 is included. A uniform monomolecular film 23 can be formed on the surface of the porous insulating film 13 thus formed.
[0026]
The cumulative type depends on many parameters such as the pH of water, the temperature, the surface pressure of the monomolecular film 23 spreading on the water surface, the descending speed and the pulling speed of the silicon substrate 11 on which the porous insulating film 13 is formed. In the case of the X-type accumulation, since the hydrophobic group 24 constituting the monomolecular film 23 adheres to the porous insulating film 13 side, the hole 14 can be closed by the hydrophobic group 24 having a size larger than that of the hole 14.
[0027]
Next, referring to FIG. 5 (g), WN _x (tungsten nitride) having a thickness of, for example, 5 nm or less, for example, 5 nm at a temperature of, for example, 350 ° C. by a CVD method using W (CO) ₆ and NH ₃ as source gases. A diffusion prevention film 26 made of a film (ride) is formed.
[0028]
Referring to FIG. 5H, a Cu plating seed layer 27 is formed on the entire surface by using a sputtering method, and then a Cu film 28 is deposited by electrolytic plating to fill the groove 15, and then a CMP (chemical mechanical polishing) method is used. The buried wiring 29 is formed by polishing until the flat portion of the porous insulating film 13 is exposed using the method described above.
[0029]
Hereinafter, although a description is omitted, a porous insulating film is formed again, a step of forming a via hole or a groove for wiring, a step of forming a monomolecular film, a step of depositing a diffusion prevention film and a conductive film for wiring, and a step of CMP. By repeating the process for the number of required wiring layers, a semiconductor integrated circuit device having multilayer wiring having a fine wiring structure can be obtained.
[0030]
As described above, in the first embodiment of the present invention, when the porous insulating film is used as the interlayer insulating film for lowering the dielectric constant, the monomolecular film is formed before the formation of the diffusion preventing film. Since it is formed on the surface of the porous insulating film, the gas for forming the diffusion prevention film does not enter the pores, and a thin diffusion prevention film can be formed with a uniform film thickness. Cu diffusion through the diffusion prevention film can be prevented.
[0031]
Next, the manufacturing process of the fine wiring according to the second embodiment of the present invention will be described. The other processes are the same as those of the above-described first embodiment, except that the monomolecular film transfer process is different. Therefore, only the step of transferring the monomolecular film is shown, and the other reference numerals used in the first embodiment are used, and illustration is omitted.
[0032]
First, a coating solution in which porogen is dispersed in methylsilsesquioxane (MSQ) serving as a matrix in a solvent is spin-coated on a silicon substrate 11 via a base insulating film 12, and then annealed at 300 to 450 ° C. Is removed and cured to form a porous insulating film 13.
[0033]
Next, after forming a groove 15 for forming a wiring by using a normal photoresist method and an etching method, the silicon substrate 11 is set perpendicular to the water surface 22 on which the uniform monomolecular film 23 is formed. Immerse in pure water 21.
[0034]
6 (a) and 6 (b). At this time, the inner surface of the groove 15 is included by using the Y-type accumulation in which the monomolecular film 23 is transferred both at the time of lowering and at the time of pulling up in the dipping step of the silicon substrate 11. A uniform monomolecular film 23 can be formed on the surface of the porous insulating film 13 thus formed.
Also in this Y-type accumulation, since the hydrophobic groups 24 forming the monomolecular film 23 adhere to the porous insulating film 13 side, the holes 14 can be closed by the hydrophobic groups 24 having a size larger than that of the holes 14.
[0035]
Thereafter, again, as in the first embodiment described above, by CVD, for example, a thickness at a temperature of 350 ° C., for example, 7 nm or less, for example, the diffusion preventing film 26 made of 5nm of WN _x After forming a film, and then forming a Cu plating seed layer 27 on the entire surface using a sputtering method, a Cu film 28 is deposited by an electrolytic plating method to fill the groove 15, and then a porous insulating film is formed using a CMP method. The buried wiring 29 is formed by polishing until the flat portion 13 is exposed.
[0036]
Next, a porous insulating film is formed again, and a step of forming a via hole or a groove for wiring, a step of forming a monomolecular film, a step of depositing a diffusion preventing film and a conductive film for wiring, and a wiring layer requiring a CMP step By repeating the above process a number of times, a semiconductor integrated circuit device having a multilayer wiring having a fine wiring structure can be obtained.
[0037]
7 (a) and 7 (b) FIG. 7 shows a step of transferring the monomolecular film 23 by Z-type accumulation for reference. In this Z-type accumulation, in the pulling-up step after immersion of the substrate, FIG. Only the monomolecular film 23 is transferred.
In this case, since the hydrophilic groups 25 smaller in size than the holes 14 forming the monomolecular film 23 adhere to the porous insulating film 13 side, the holes 14 cannot be closed by the monomolecular film 23, and In the step of forming the diffusion preventing film, the gas enters the hole 14.
[0038]
The embodiments of the present invention have been described above. However, the present invention is not limited to the configurations and conditions described in the embodiments, and various changes can be made.
For example, in the above embodiments, although the porous insulating film formed by using the MSQ, HSQ (Hydrogen Silsesquioxane) or SiLK ^{T. M.} (Trade name of Dow Chemical Company) or the like may be used.
The porogen to be added has various materials from various companies.
[0039]
Further, the method of forming the porous insulating film is not limited to the spin coating method, and a porous insulating film having a chemical composition of SiOC may be formed by using a CVD method.
[0040]
Further, a fine structure in the form of clusters is applied, followed by firing to remove the solvent and to combine the clusters to form a porous insulating film.
[0041]
Further, in each of the above embodiments, WN _x is used as the diffusion prevention film. However, the invention is not limited to WN _x , and TaN _x (tantalum nitride) may be used.
[0042]
When this TaN _x is formed, the film may be formed by a CVD method at 350 ° C. using TaBr ₅ and NH ₃ as source gases, or a plasma CVD method in which H ₂ or N ₂ is further mixed. The reaction may be promoted.
[0043]
In each of the above embodiments, the monomolecular film is formed from (t-butyl) ₄ H ₂ Pc which is a compound of phthalocyanine (Pc) and a butyl group (butyl). The invention is not limited thereto, and a monomolecular film composed of various kinds of hydrophobic groups and hydrophilic groups may be used. Any size may be used as long as the size of the hydrophobic group is larger than the pore diameter.
[0044]
For example, as the hydrophobic group, a compound of oxygen, carbon, fluorine and nitrogen may be used.Specifically, even if a fluorocarbon, a saturated hydrocarbon, an aromatic hydrocarbon, a nitrate or the like is used. Good thing.
[0045]
Further, in each of the above-described embodiments, the process of forming the buried wiring layer is described. However, the present invention is also applied to a case where a Cu film is formed flat and then a wiring is formed by patterning.
[0046]
Further, in each of the above-described embodiments, the description has been given as a manufacturing process of a semiconductor device. However, the present invention is not limited to a semiconductor device, and may be applied to a ferroelectric device such as an optical polarizing element or an optical deflecting element. The present invention is also applied to a wiring forming process of another electronic device.
[0047]
Further, in each of the above embodiments, the porous insulating film is described as an interlayer insulating film. However, the present invention is not limited to the interlayer insulating film, and is also applicable to a case where the wiring is a single layer. For example, the present invention is also applied to a process of forming a coplanar wiring forming a distributed constant circuit or the like.
[0048]
Here, referring to FIG. 1 again, the detailed features of the present invention will be described again.
Again referring to FIG. 1 (Appendix 1), the method includes a step of uniformly forming a thin film on the surface of the porous insulating film 2 and a step of sequentially forming a diffusion prevention film 8 and a wiring conductive film 9 via the thin film. A method for forming a fine wiring structure.
(Supplementary Note 2) After the thin film is formed as a uniform monomolecular film 4 on the surface of the solution, at least the porous insulating film 2 is immersed in the solution to uniformly form the monomolecular film 4 on the surface of the porous insulating film 2. The method for forming a fine wiring structure according to claim 1, wherein the fine wiring structure is formed.
(Supplementary Note 3) The method for forming a fine wiring structure according to Supplementary Note 1 or 2, wherein the monomolecular film 4 includes a combination of a hydrophilic group 6 and a hydrophobic group 5.
(Supplementary note 4) The method for forming a fine wiring structure according to supplementary note 3, wherein the hydrophobic group 5 is a compound of silicon, oxygen, carbon, fluorine, and nitrogen.
(Supplementary Note 5) The method for forming a fine wiring structure according to Supplementary Note 4, wherein the hydrophobic group 5 is formed of phthalocyanine, and the hydrophilic group 6 is formed of butyl group.
(Supplementary Note 6) The formation of the fine wiring structure according to any one of Supplementary Notes 3 to 5, wherein a diameter of the hydrophobic group 5 in a major axis direction is larger than a diameter of the hole 3 of the porous insulating film 2. Method.
(Supplementary Note 7) The formation of the fine wiring structure according to any one of Supplementary Notes 3 to 6, wherein the monomolecular film 4 is attached to the surface of the porous insulating film 2 by X-type accumulation or Y-type accumulation. Method.
(Supplementary Note 8) An electronic device, wherein a wiring 7 composed of a diffusion prevention film 8 and a conductive film 9 for wiring is provided on a porous insulating film 2 via a monomolecular film 4.
[0049]
【The invention's effect】
According to the present invention, before forming the diffusion prevention film, since the surface of the porous insulating film is covered with the monomolecular film and the pores are closed with the hydrophobic groups, the diffusion prevention film enters the porous insulating film. It is possible to form a diffusion prevention film uniformly without any problems, and to improve wiring performance without impairing a low dielectric constant, which is one of the characteristics of the porous insulating film, and thus, has a fine wiring structure. This greatly contributes to improvement in the reliability of electronic devices such as semiconductor integrated circuit devices.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a basic configuration of the present invention.
FIG. 2 is an explanatory diagram of a forming process up to a halfway point in the first embodiment of the present invention.
FIG. 3 is an explanatory view of a forming process of the first embodiment of the present invention up to the middle after FIG. 2;
FIG. 4 is an explanatory diagram of a forming process of the first embodiment of the present invention up to the middle of FIG. 3;
FIG. 5 is an explanatory diagram of a forming process after FIG. 4 in the first embodiment of the present invention.
FIG. 6 is an explanatory diagram of a monomolecular film transfer step according to a second embodiment of the present invention.
FIG. 7 is an explanatory diagram of a monomolecular film transfer step by Z-type accumulation.
FIG. 8 is an explanatory diagram of wiring width dependence of wiring specific resistance.
FIG. 9 is an explanatory diagram of a problem when a diffusion prevention film is provided directly on a porous insulating film.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 substrate 2 porous insulating film 3 hole 4 monomolecular film 5 hydrophobic group 6 hydrophilic group 7 wiring 8 diffusion preventing film 9 conductive film for wiring 11 silicon substrate 12 base insulating film 13 porous insulating film 14 hole 15 groove 21 pure water 22 Water surface 23 Monomolecular film 24 Hydrophobic group 25 Hydrophilic group 26 Diffusion prevention film 27 Cu plating seed layer 28 Cu film 29 Wiring 41 Porous insulating film 42 Ta film 43 Hole

Claims (5)

A method for forming a fine wiring structure, comprising: a step of forming a thin film uniformly on the surface of a porous insulating film; and a step of sequentially forming a diffusion prevention film and a conductive film for wiring via the thin film. After forming the thin film as a uniform monomolecular film on the solution surface, at least the porous insulating film is immersed in the solution to form a uniform monomolecular film on the surface of the porous insulating film. A method for forming a fine wiring structure according to claim 1. 3. The method according to claim 1, wherein the monomolecular film comprises a combination of a hydrophilic group and a hydrophobic group. 4. The method according to claim 3, wherein the hydrophobic group is a compound of silicon, oxygen, carbon, fluorine and nitrogen. The method for forming a fine wiring structure according to claim 3, wherein a diameter of the hydrophobic group in a major axis direction is larger than a pore diameter of the porous insulating film.

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