KR100865724B1 - Method for atomic layer deposition of copper layer - Google Patents

Abstract

The present invention provides an atomic layer deposition method of a copper film suitable for overcoming the difficulty of forming a thin seed layer by physical vapor deposition and chemical vapor deposition while preventing contamination of the wafer and surface oxidation. Making a step; Supplying a copper precursor into the reactor to chemisorb the copper precursor onto the substrate; Purging the unreacted copper precursor of the copper precursor; Supplying a hydrogen atom beam into the reactor to induce a reaction with the chemisorbed copper precursor to deposit a copper film; And purging the reaction byproduct of the copper precursor and the hydrogen atom beam.

Copper film, atomic layer deposition, copper precursor, hydrogen atom beam

Description

Method for atomic layer deposition of copper layer             

1 is a timing diagram for explaining an atomic layer deposition method of a copper film according to an embodiment of the present invention;

2 is a diagram showing the surface reaction of a copper-organic compound and a hydrogen atom beam;

Figure 3 is a mass spectrum diagram of the desorption species generated and desorbed when hydrogen atoms are injected into the surface of Cu (hfac) adsorbed,

4 is a structural diagram of an apparatus for performing atomic layer deposition of a copper film;

5A to 5C are cross-sectional views illustrating a method of forming a copper wiring according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

21 substrate 22 interlayer insulating film

23: damascene pattern 24: diffusion barrier layer

25 copper seed layer 26 copper film

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to an atomic layer deposition method of a copper film.

As the integration density of semiconductor devices increases, limitations and necessity of improvement of materials and processing methods of metal wirings are emerging, and many researches and developments are being conducted. As one axis of the development direction, a process method called copper wiring has been proposed.

As a method of forming copper wiring, physical vapor deposition (PVD), chemical vapor deposition (CVD) or electrical methods (electroplating, electrodeless deposition) and the like are known. .

However, physical vapor deposition (PVD) has a problem of very poor landfill characteristics, and chemical vapor deposition (CVD) has a problem of forming a thin film having a very rough deposition rate and a very rough surface. Because it is made in the contained aqueous solution, there is a problem in that a seed layer, which is a conductive material, must be formed on the entire surface of the wafer in advance, along with problems of contamination, oxidation of the surface, and low yield. In particular, there is a need for a technique that deposits the seed layer very thin and conformally due to the reduction in line width and the increase in aspect ratio of the contact / via holes. Since the seed layer is difficult to be formed by physical vapor deposition and thinly formed by general chemical vapor deposition, a new process method for forming a seed layer is required.

The present invention has been made to solve the above problems of the prior art, and the atomic layer deposition method of the copper film suitable for overcoming the difficulty of forming a thin seed layer by physical vapor deposition and chemical vapor deposition while preventing contamination of the wafer and surface oxidation. The purpose is to provide.

Atomic layer deposition of the copper film of the present invention for achieving the above object comprises the steps of loading a substrate in a reactor; Supplying a copper precursor into the reactor to chemisorb the copper precursor onto the substrate; Purging the unreacted copper precursor of the copper precursor; Supplying a hydrogen atom beam into the reactor to induce a reaction with the chemisorbed copper precursor to deposit a copper film; And purging the reaction by-product of the copper precursor and the hydrogen atom beam.

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. .

The present invention to be described later is a technique of applying the atomic layer deposition method (ALD) to the copper wiring process. At least two compounds are required for atomic layer deposition, and the compounds are injected into the reactor in the form of pulses and chemically adsorbed to the surface, and only the desired substances are formed on the surface by reacting only with the adsorbate and the next reactant. They must be completely removed from the surface and evacuated.

It is difficult to apply atomic layer deposition to deposit monoatomic metals such as copper or tungsten. Among them, it is difficult to adopt two or more reactants capable of depositing a desired material by reacting only on the surface with a subsequent chemically adsorbed surface at the same time, and moreover, it is difficult to adopt reactants that can be made at low temperatures.

The reactants employed in the present invention are well known copper precursors applied in metalorganic chemical vapor deposition (MOCVD) processes. The copper precursor is a copper-organic (Cu-Org) compound in which an organic (Org) is bonded to a copper element (Cu).

For example, copper II, such as Cu (hfac) ₂ compound with low vapor pressure, has higher vapor pressure than copper II and copper II compounds, resulting in faster deposition rates and high purity copper thin film deposition at low temperatures of 150 ° C to 250 ° C. A copper I (Cu I) compound is used which makes it possible. Among the various copper I compounds developed so far, (hfac) Cu (TMVS) compounds exist in liquid phase at room temperature and enable the deposition of high-purity copper thin films at low temperatures. to be.

In the examples described below, a hydrogen atom beam is used as a reducing material reacting with the copper precursor without requiring a separate copper precursor for atomic layer deposition using a well-known copper precursor.

1 is a timing diagram illustrating an atomic layer deposition method of a copper film according to an embodiment of the present invention.

Referring to Figure 1, after loading a substrate to be a copper film it is deposited in the reactor, copper during the T ₁ time in the reactor - to supply the organic compound of copper to the substrate surface-adsorbed chemical compounds of organic matter.

Subsequently, in order to remove the unreacted copper-organic compound, after supplying an inert gas such as argon and nitrogen as a purge gas for T ₂ hours, a hydrogen atom beam as a reducing gas is supplied into the reactor for T ₃ hours.

Next, an inert gas such as argon and nitrogen is supplied as a purge gas for T ₄ hours to remove the reaction byproduct.

The process of supplying the copper-organic compound, purge, hydrogen atom beam supply, and purge of FIG. 1 is one cycle, and the process is repeated for a desired cycle to deposit a copper film having a desired thickness.

2 is a diagram showing the surface reaction of a copper-organic compound and a hydrogen atom beam.

Referring to FIG. 2, when the hydrogen atom beam (H) is supplied in a state in which the copper-organic compound (Cu-Org) is chemisorbed on the surface of the substrate, the organic material (Org) and hydrogen in the copper-organic compound (Cu-Org) are hydrogenated. The atoms (H) react to form volatile reactants (Org-H), and only the copper film (Cu) remains on the substrate surface.

The copper-organic compound, which is a copper precursor (Cu-precursor) applied in FIGS. 1 and 2, is Cu (I)-(β-dikenonate) -L (L is a Lewis ligand) or copper II, in which copper I is a compound. Cu (II)-(β-dikenonate) ₂ as a compound is used.

In general, copper precursors are largely divided into +1 and +2 valent compounds. Copper-organic compounds chemisorb in the form of Cu- (β-dikenonate) on the wafer surface under high vacuum. Or organic matters decompose to contaminate the surface.

However, when the surface chemisorbed with Cu- (β-dikenonate) is exposed to a hydrogen atom beam, the (β-dikenonate) group forms β-diketone and the surface becomes above a certain temperature. Detachable and exhausted from

FIG. 3 is a mass spectrum diagram of desorption species generated and desorbed when hydrogen atoms are injected onto Cu (hfac) -adsorbed surfaces, and Cu (hfac) (vtms) [hfac = hexafluoroacetyacetonate, vtms = vinyltrimethylsilane) was used.

The result of FIG. 3 is QMS (Quadrupole) for the desorption species which first do a small amount of Cu (hfac) (vtms) onto the copper surface and adsorb the hydrogen atom beam onto the surface while desorbing only Cu (hfac). Spectrum analyzed simultaneously with Mass Spectrometer.

As shown in FIG. 3, Cu (hfac) is when the introduction of hydrogen atoms to the substrate surface adsorbed is generated and desorbing Dhfac, mass spectrum (mass spectrum) CF ₃ in the degradation products of CF ₃ groups Dhfac of Dhfac in Dhfac-CF ₃ is desorbed. In other words, it can be seen that the hfac group reacts with the hydrogen atom to generate and desorb H-hfac from the surface, leaving only copper atoms on the surface.

On the other hand, a method of supplying hydrogen atoms is a method of decomposing the heated copper tube or copper wire into atoms by heat while passing through the hydrogen molecules when atomic layer deposition is performed in a small region.

Another method is to apply a remote plasma to a wafer used for a large semiconductor.

4 is a structural diagram of an apparatus for performing atomic layer deposition of a copper film, which has a shower head 10 on a wafer, which forms a hydrogen atom by entering an inlet 11 to which a copper precursor and a reducing gas are supplied and a hydrogen molecule. Separation of the injection hole 12 is designed to be discharged from each of the other discharge holes (13,14). Here, the hydrogen atom is generated by the remote plasma, and is obtained by decomposing the hydrogen molecule into the hydrogen atom in the hydrogen atom generator 15 by a method such as RF (Radio Frequency) plasma. In order for the hydrogen atom generated by the remote plasma to reach the wafer surface stably, high vacuum of 10 ^-3 torr to 10 ^-8 torr is required.

Meanwhile, as the copper precursor, a copper halogen compound may be used in addition to the copper-organic compound, and the reactor in which the atomic layer deposition of the copper film is carried out maintains a low temperature of room temperature to 300 ° C.

5A to 5C are cross-sectional views illustrating a method of forming a copper wiring according to an embodiment of the present invention.

As shown in FIG. 5A, an interlayer insulating film 22 is formed on the substrate 21 on which various elements for forming a semiconductor device are formed, and by a single damascene or a dual damascene method. A damascene pattern 23 consisting of vias and / or trenches is formed. Thereafter, cleaning is performed to remove by-products generated when the damascene pattern 23 is formed.

Here, the interlayer insulating film 22 is formed of an insulating material having a low dielectric constant (low k). In the cleaning process, RF plasma can be used when the underlying layer of the damascene pattern 23 is a metal such as tungsten or aluminum, and reactive cleaning is applied when the underlying layer is copper. do.

As shown in FIG. 5B, a barrier metal layer 24 is formed on the surface of the interlayer insulating layer 22 including the damascene pattern 23. At this time, the diffusion barrier layer 24 may be a PVD TiN, CVD TiN, or MOCVD TiN thin film, PVD Ta, PVD TaN, CVD Ta, CVD TaN, CVD WN, PVD TiAlN, PVD TiSiN, PVD TaSiN, CVD TiAlN, CVD TiSiN, Application of CVD TaSiN thin films is possible.

Next, a thin copper seed layer 25 is deposited on the diffusion barrier layer 24 according to the timing diagram shown in FIG. 1. At this time, by using the atomic layer deposition method, even if the aspect ratio of the damascene pattern is large, it is possible to deposit the copper seed layer 25 uniformly without overhang or void (void).

Next, the copper film 26 is deposited by depositing copper on the copper seed layer 25 until the damascene pattern 23 is embedded by an electroplating method or an electroless plating method. To form.

As shown in FIG. 5C, the copper film 26, the copper seed layer 25, and the diffusion barrier layer 24 are polished until the surface of the interlayer insulating film 22 is exposed by chemical mechanical polishing. A copper wiring 26a is formed in the damascene pattern 23. At this time, the diffusion barrier layer 24a and the copper seed layer 25a also remain in the damascene pattern 23.

According to the above-described embodiment, since the copper seed layer 25 is deposited using atomic layer deposition, the step coverage is close to 100%, and the atomic layer deposition method is a lower temperature process than chemical vapor deposition, as is well known, and the surface roughness. It is possible to form a very thin smooth film, and suppresses the occurrence of defects such as bridges and thinnings of the copper wiring 26a.

Metal organic chemical vapor deposition (Metal Organic CVD) of a copper film is conventionally performed only under low vacuum of several mtorr to several tens of torr, and it is known that chemical vapor reaction cannot be performed at a pressure of 0.01 mtorr or less. However, the present invention can eliminate impurity contamination on the wafer since the pressure in the atomic layer deposition chamber can be made to be the same as in a high vacuum atmosphere in which a conventional physical vapor deposition (PVD) process is performed.

Although the technical spirit of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, the present invention can completely fill holes having a large aspect ratio, so that the defects can be reduced since the process proceeds without voids in subsequent chemical mechanical polishing processes such as dual damascene.

In addition, since the thickness can be adjusted to a very thin thickness, it can be used as a seed layer of the electrical deposition process, and can proceed under high vacuum, thereby preventing contamination and oxidation of the wafer.

In addition, since the hydrogen atom beam is used as the reducing material, the impurity content in the copper film can be lowered, and thus there is an effect of forming a copper wiring having very low specific resistance and high EM (ElectroMigration) resistance even in subsequent heat treatment.

Claims (7)

Loading a substrate into the reactor; Supplying a copper precursor into the reactor to chemisorb the copper precursor onto the substrate; Purging the unreacted copper precursor of the copper precursor; Supplying a hydrogen atom beam into the reactor to induce a reaction with the chemisorbed copper precursor to deposit a copper film; And Purging the reaction by-product of the copper precursor and the hydrogen atom beam Atomic layer deposition of a copper film comprising a. delete The method of claim 1, The hydrogen atom beam is heated by heating a copper tube or copper wire to decompose hydrogen molecules into hydrogen atoms and supply. The method of claim 1, And the hydrogen atom beam is supplied by using a remote plasma. The method of claim 1, The copper precursor is an atomic layer deposition method of a copper film using a copper-organic compound or a copper halogen compound. The method of claim 1, Wherein the reactor maintains a high vacuum of 10 ^-3 torr to 10 ^-8 torr. Forming an interlayer insulating film on the substrate; Etching the interlayer insulating film to form a damascene pattern; Forming a diffusion barrier layer on a front surface of the damascene pattern; Forming a copper seed layer on the diffusion barrier layer by atomic layer deposition; Forming a copper film on the copper seed layer through an electrical deposition method; And Performing chemical mechanical polishing until the surface of the interlayer insulating film is exposed to form copper wiring in the damascene pattern, Forming the copper seed layer, Chemically adsorbing a copper precursor, purging an unreacted copper precursor of the copper precursor, supplying a hydrogen atom beam to induce a reaction with the chemisorbed copper precursor, and depositing a copper film; and Purging the reaction byproduct of the hydrogen atom beam Method of forming copper wiring.

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