WO2000013207A2

WO2000013207A2 - Method for forming a metal film

Info

Publication number: WO2000013207A2
Application number: PCT/KR1999/000500
Authority: WO
Inventors: Won-Yong Koh; Sang-Won Kang
Original assignee: Genitech Co., Ltd.
Priority date: 1998-09-01
Filing date: 1999-09-01
Publication date: 2000-03-09
Also published as: KR20000018353A; KR100332364B1; WO2000013207A3

Abstract

A method for forming a metal film for use in semiconductor devices on a substrate. A catalyst metal layer for facilitating formation of a metal film is formed first on a substrate using thermal chemical vapor deposition. Then, at least one source of the metal film is prepared as a gas phase. The metal film is formed on the catalyst metal layer by applying the gas phase source to the catalyst metal layer. According to the present invention, a metal film of uniform thickness can be formed on an uneven substrate surface or on a hole with a high aspect ratio.

Description

METHOD FOR FORMING A METAL FILM

TECHNICAL FIELD

The present invention relates to a method for forming a film, and more particularly, to a method for forming a metal film for use in semiconductor devices on a substrate.

BACKGROUND ART

In the manufacture of semiconductor devices, metal films are used for circuit interconnections. One of the materials widely used in forming such a metal film is aluminum, and tungsten is used for specific applications. However, it is expected that copper, the second most conducting metal, will be increasingly used henceforth instead of aluminum.

Circuit interconnection formation is divided into two categories: formation of contacts and formation of interconnection. As the sizes of integrated circuit structures have continued to become smaller and smaller, problems have arisen with the conventional circuit interconnection formation, particularly in the formation of narrow lines or metal contacts. One of the problems is that the formation of a metal film of uniform thickness over an uneven surface becomes more difficult with the tight design rule. Another problem is that metal films deposited by a conventional method can not completely fill a contact or via hole having a high aspect ratio without voids.

However, if the deposition rate of a film is controlled only by the rate of surface chemical reaction independent of the mass transport rate at which the deposition sources travel to the surface of the substrate, a contact or via hole having a high aspect ratio can completely be filled with a perfect step coverage.

It is well known in the field of chemistry that higher chemical reaction rate at the same temperature or the same reaction rate at lower temperature can be accomplished with the use of a catalyst. However, up to now examples of catalyst applications in forming metal films of semiconductor devices have been limited to few cases. For example, S. J. Potochnik et al., in an article entitled "Selective Copper Chemical Vapor Deposition (CVD) Using Pd-activated Organosilane Films", published on pl841 of Langmuir, Vol. 11, No. 6, in 1994, reported that a copper metal film could selectively be chemical-vapor-deposited only on portions of a diamond substrate where a palladium ion catalyst is introduced. In the process, (l,l,l,5,5,5-hexafluoro-2,4-pentanedionato) copper(I)-trimethylvinylsilane was used as a deposition source and the deposition temperature was in the range of 171-183°C. The process comprises the steps of: oxidizing the surface of a diamond substrate; dipping the substrate into an aminosilane solution to fix amino groups on the surface of the substrate; irradiating the substrate through a mask with ultraviolet (UV) light to selectively remove the fixed amino groups from the substrate, resulting in a fixed amino group pattern; fixing palladium catalyst on the pattern; and chemical vapor depositing a copper film only on the pattern. They also reported the process was applied to a substrate such as silicon or quartz instead of the diamond substrate. However, their process requires solution treatments to introduce the patterned palladium catalyst onto the substrate, causing difficulties when incorporated with other vacuum process.

O. Gottsleben et al., in an article entitled "Two-step Generation of Aluminum Microstructures on Laser-generated Pd Pre-nucleation Patterns Using Thermal CVD from (Trimethylamine)trihydridoaluminum", published on p201 of Advanced Materials, Vol. 3, No. 4, in 1991, reported that aluminum microstructures were selectively formed only on a palladium catalyst metal pattern using chemical vapor deposition using (trimethylamine)trihydridoaluminum as a CVD source. In this process, the palladium catalyst metal pattern was generated by an UV excimer laser.

O. Lehmann et al. applied liquid triethylamine alane to a KrF-laser patterned palladium catalyst layer formed on an alumina substrate, forming an aluminum film selectively on the patterned palladium catalyst layer. (Reference : O. Lehmann and M. Stuke, "Liquid Precursor Two-step Aluminum Thin-film Deposition on KrF-laser patterned palladium", Applied Physics Letters, Vol. 61, No. 17, p 2027, 1992.)

As described above, O. Gottsleben et al. formed a palladium metal layer by decomposing precursors using a laser, and O. Lehmann et al. also used laser photo- CVD in their method. However, according to the above methods, formation of a uniform catalyst layer on an uneven surface is impossible because the inner side surface of a hole or a groove can not be evenly irradiated. V. Bhaskaran et al., in an article entitled "Palladium Thin Films Grown by CVD from (l,l,l,5,5,5-hexafluoro-2,4-pentanedionato)Palladium(II)", published on p85 of Chemical Vapor Deposition, Vol. 3, No. 2, in 1997, reported that a pure palladium layer was obtained by applying both (l,l,l,5,5,5-hexafluoro-2,4- pentanedionato)Palladium(II) and hydrogen gas to a silicon single crystal substrate heated at a temperature between 80-200°C. The purity of palladium layer was such that carbon, fluorine, or oxygen was not detected when investigated by Auger electron spectroscopy. In the process, nitrogen gas was used as a carrier gas of a sublimated palladium source compound instead of hydrogen gas to avoid the violent reaction between hydrogen gas and palladium source compound. However, in this case, they reported that the inside of gas conduit, where the palladium source compound carried nitrogen gas and hydrogen gas meet, should be frequently cleaned because palladium layers are deposited thereon. In general, superior step coverage is not expected to occur under violent chemical vapor reaction conditions. The article is accompanied by a photograph showing the cross section of a palladium layer which is deposited on grooves of a width of 0.5 μm and a depth of 2.0μm. Referring to the photograph, it is found that the palladium layers deposited on the top of grooves are more than five times thicker than those deposited on the underside.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide a method for forming a metal film of uniform thickness despite unevenness of a substrate surface.

In order to accomplish the aforementioned object, the present invention provides a method for forming a metal film, comprising the steps of: (a) forming a catalyst metal layer on a substrate using thermal chemical vapor deposition to facilitate formation of the metal film; (b) preparing at least one source of the metal film as a gas phase; and (c) applying the gas phase source to the catalyst metal layer to form a metal film thereon.

In the embodiments of the present invention, palladium or platinum may be used as the catalyst metal for facilitating formation of a metal film comprising aluminum or copper. The formation of catalyst metal layers can be repeated to increase the deposition rate of the metal film. If more than two source gases are required to form the catalyst metal layer, it is desirable to supply the source gases sequentially on the substrate, not to supply the source gases simultaneously thereon, to obtain a catalyst metal layer with a superior step coverage. Additionally, during or after the deposition of the metal film, it is also desirable to diffuse the catalyst metal into the metal film to form an alloy film.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to ID show the steps of forming a metal film in accordance with an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the practice of the invention, a silicon substrate 10 to form a metal film thereon is prepared first. Then, as shown in FIG. 1A, a palladium thin layer 20 is formed on the silicon substrate by supplying both (l,l,l,5,5,5-hexafluoro-2,4- pentanedionato)Palladium(II) and hydrogen gas sequentially on the silicon substrate. In other embodiment, platinum may be employed instead of the palladium.

In particular, a Pd-Al alloy or a Pd-Cu alloy provides the following advantages. If pure aluminum is employed to form interconnection of semiconductor devices, low current density should be maintained to avoid an electromigration- induced open circuit. Accordingly, in a conventional method, an Al-Cu alloy, in which aluminum contains a small amount of copper, is used as an interconnection material to decrease electromigration. The Pd-Al alloy can decrease electromigration thus increase the durability of the metal interconnection, to a degree equal or superior to the Al-Cu alloy. A Pd-Al alloy displays other desirable properites. K. P. Rodbell et al. reported that it is resistant to metal corrosion during a reactive ion etching process in "The Microstructure, Mechanical Stress, Texture and Electromigration Behavior of Al-Pd alloys", Journal of Electronic Materials, Vol. 22, No. 6, p 597, 1993. Additionally, P. Atanasova et al. reported that a Cu-0.5% Pd alloy effectively prevented the oxidation of copper without causing any effects on electrical conductivity. (Reference : P. Atanasova, V. Bhaskaran, T. Kodas and M. Hampden- Smith, an article entitled "Oxidation Resistance of Copper Alloy Thin Films Formed by CVD" published in a book "Advanced Metallization for Future ULSI", Materials Research Society, 1996 of K. N. Tu, J. W. Mayer, J. M. Poate and L. J. Chen.) Therefore, if palladium catalyst is diffused into an interconnection metal film to form an alloy during or after the deposition of the metal film, additional process is not needed to prevent electromigration or oxidation of the interconnection metal film. In the embodiment of the present invention, the palladium layer 20 is formed as thin as possible with a uniform thickness to provide higher current density, because the sheet resistance of catalyst metal is generally higher than that of aluminum or copper for use in the interconnection. For this purpose, a uniform thickness palladium layer is formed by atomic layer deposition in which source compound gases are sequentially supplied on the silicon substrate maintained at a temperature lower than the thermal decomposition temperatures of source compound gases. In this process, only surface reaction is utilized while chemical vapor reaction between source gases is prevented. In general, the deposition rate of atomic layer deposition is significantly low compared with that of conventional deposition where source gases are simultaneously supplied. However, in this embodiment, such a low deposition rate is advantageous because a thin palladium catalyst layer is required. In view of the report of S. J. Potochnik et al. that palladium ion catalyst of less than one atomic layer induces effective chemical deposition of copper, a palladium thin layer of several atomic layers is expected to provide sufficient catalytic effects. The sources required to form an aluminum film are prepared as gases. After formation of a palladium catalyst layer, the source gases are applied to the palladium catalyst layer to form an aluminum film 20 thereon, as shown in FIG. IB. In the course of chemically depositing the aluminum film, the palladium catalyst is diffused into the aluminum film by applied heat, forming an Al-Pd alloy. If the Al-Pd alloy is used as an interconnection metal material, no additional process is needed to prevent electromigration or oxidation of the interconnection metal film and turn-around-time can be considerably reduced. The Al-Pd alloy can be formed in a different way when the heat applied during the chemical deposition of aluminum film is insufficient for the diffusion of the palladium catalyst. In this case, additional heat treatment is conducted after the formation of aluminum film. And then, formation of an additional palladium catalyst layer 22 and an additional aluminum film 32 is sequentially repeated as shown in FIG. 1C and ID. As such, the multiple palladium catalyst layers are used upon consideration of the study of O. Lehmann and M. Stuke. They reported that the thickness of aluminum film formed on the palladium layer did not increase and came to saturation with increasing contact time between a liquid aluminum source and the palladium layer. It is supposed that this results from the reduction in catalytic effect of the palladium catalyst underlying the metal film. In an effort to overcome the above problem, multiple palladium catalyst layers are used to the overall deposition rate of the metal film.

Claims

WHAT IS CLAIMED IS :

1. A method for forming a metal film comprising the steps of:

(a) forming a catalyst metal layer on a substrate using thermal chemical vapor deposition to facilitate formation of said metal film;

(b) preparing at least one source of said metal film as a gas phase; and

(c) applying said gas phase source to said catalyst metal layer to form a metal film thereon.

2. The method of claim 1, wherein said catalyst metal layer comprises palladium or platinum.

3. The method of claim 1 , wherein said metal film comprises aluminum or copper.

4. The method of claim 1, after the step (c), further comprising the steps of:

(d) forming another catalyst metal layer on said metal film;

(e) preparing at least one source of said metal film as a gas phase; and

(f) applying said gas phase source to said another catalyst metal layer to form another metal film thereon.

5. The method of claim 4, wherein the steps (d) to (f) are repeated at least one number of times.

6. The method of claim 1, wherein the deposition source of said catalyst metal layer comprises at least two source gases, said source gases being alternately applied to said substrate to reach a desired thickness during the step (a).

7. The method of claim 2, wherein the deposition source of said catalyst metal layer comprises at least two source gases, said source gases being alternately applied to said substrate to reach a desired thickness during the step (a).

8. The method of claim 3, wherein the deposition source of said catalyst metal layer comprises at least two source gases, said source gases being alternately applied to said substrate to reach a desired thickness during the step (a).

9. The method of claim 4, wherein the deposition source of said catalyst metal layer comprises at least two source gases, said source gases being alternately applied to the underlying structure to reach a desired thickness during the step (d).

10. The method of claim 5, wherein the deposition source of said catalyst metal layer comprises at least two source gases, said source gases being alternately applied to the underlying structure to reach a desired thickness during the step (d).

11. The method of claim 1, wherein the step (c) includes diffusing said catalyst metal layer into said metal film to form an alloy film.

12. The method of claim 11, wherein said catalyst metal layer comprises palladium.

13. The method of claim 11, wherein said metal film comprises aluminum or copper.

14. The method of claim 1, after the step (c), further comprising the step of diffusing said catalyst metal layer into said metal film to form an alloy film.

15. The method of claim 14, wherein said catalyst metal layer comprises palladium.

16. The method of claim 14, wherein said metal film comprises aluminum or copper.