JP2645811B2 - Method for forming electrode of semiconductor device having diffusion barrier function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an electrode of a semiconductor device, and more particularly to a method for forming a dielectric electrode having a pervoskite structure having excellent diffusion barrier characteristics and contact characteristics. In particular, Pt, Pd
In a dielectric using a near noble metal, a transition group IVB or VB group metal and a transition group VIII group metal are heat-treated in an atmosphere of NH ₃ to have a large crystal grain size and a crystal grain boundary. The present invention relates to a method for forming a lower electrode having excellent diffusion barrier characteristics and contact characteristics by forming a high melting point nitride film filled with oxygen therebetween.

[0002]

2. Description of the Related Art Copper and other metals are used as next-generation wiring materials.
PZT (PbZr _x Ti _1-x O ₃ ) or BST (BaSrT
iO ₃ ) has been spotlighted as a next-generation dielectric material. However, since these may induce a leak or the like from the reaction with the silicon substrate, a diffusion barrier is required to prevent this.

[0003] Copper diffusion barriers are Co, Cr, Pd, Ti.
N, NbN and the like are well known as excellent ones. Furthermore, pervoskits such as BST and PZT
e) As a dielectric electrode material having a structure, a near-noble metal such as Pt or Pd, which is a transition group VIII metal, or a conductive oxide film such as RuO ₂ is mainly used. In order to suppress the mutual diffusion and increase the adhesive force, a Ti layer or a TiN layer must be formed between the electrode and the substrate.

A diffusion barrier formed between such an electrode or a substrate and the electrode must satisfy the following conditions. 1. It must be stable so as not to react with copper or a ferroelectric used as an electrode, and must have high oxidation resistance and excellent electric conductivity. 2. The material used as the diffusion barrier must have good adhesion to the substrate. Conventionally, near noble metals of transition group VIII or chromium Cr are used as capacitor electrodes. These metals have strong oxidation resistance, low reactivity, are stable, and have excellent electrical conductivity. However, there was a disadvantage that the barrier properties were weak.

[0005] The transition group VB or IVB group high melting point metal has excellent adhesion to a silicon substrate or a silicon oxide film.
Refractory metal nitrides have excellent diffusion barrier properties and electrical conductivity properties.

FIG. 9 shows a structure of a conventional capacitor electrode using a Perboss kit dielectric. Referring to FIG. 9, a capacitor electrode using a conventional Pelboss kit dielectric is:
A Ti barrier film 92 for a diffusion barrier is deposited on a silicon substrate or a silicon oxide film 91, a dielectric film 94 of a Perboss kit is formed on the Ti film 92, and a lower electrode 93 and an upper electrode are formed above and below the dielectric film. 95 has a structure in which a Pt film of a near noble metal is formed.

The conventional heat treatment process is divided into a pre-purge stage, a heating stage, an annealing stage, a cooling stage, and a purge stage as shown in FIG. 8, and the heat treatment process is performed in an N ₂ atmosphere from the pre-purge stage to the purge stage. And in an annealing step only in an NH ₃ atmosphere, and in other steps in an N ₂ atmosphere.

[0008]

However, both of the above two methods are performed in an N ₂ atmosphere in the pre-purge step, but the conventional capacitor structure shown in FIG. 9 performs a heat treatment step in an N ₂ atmosphere in the pre-purge step. Also, without forming a titanium nitride film at the boundary between the Pt film of the lower electrode 93 and the diffusion barrier Ti film 92, nitrogen is mixed at the boundary as shown in FIG. 6 to prevent high-temperature diffusion of the upper Pt. There has been a problem that a role as a possible diffusion barrier cannot be sufficiently fulfilled.

This is the same as when the capacitor electrode is formed on the silicon oxide film. However, when the heat treatment is performed in the N ₂ atmosphere in the pre-purge step, as shown in FIG. Since a titanium nitride film is not formed at the boundary with the Ti film 92 and nitrogen is mixed at the boundary, there is a problem that a sufficient role as a diffusion barrier cannot be achieved. The conventional capacitor electrode is P
When t, Pd, or the like is used as an electrode, a noble metal (dilute noble metal) is used, resulting in an increase in price and
When uO ₂ or the like is used as an electrode, there is a difficulty in a patterning step or the like because RuO ₂ is unstable.

It is an object of the present invention to provide a method for forming a capacitor electrode of a semiconductor device having not only excellent diffusion barrier characteristics but also excellent contact characteristics using a usual apparatus for forming a capacitor electrode.

Another object of the present invention is to provide a method for forming a capacitor electrode of a semiconductor device having not only excellent diffusion barrier properties but also excellent adhesion to a substrate by using an ordinary apparatus for forming a capacitor electrode. It is in.

[0012]

According to the present invention, there is provided a method of forming an electrode having a diffusion barrier function, comprising the steps of: forming a transition group IVB refractory metal film such as Ti, Zr, or Hf on a silicon substrate; And Fe, Co, Ni, Ru, Rh, P
sequentially depositing a transition group VIII near noble metal film such as d, Os, Ir, Pt, etc., and performing a heat treatment process in an ammonia atmosphere from a pre-purge stage to a transition group IVB metal film and a transition group VIII group. Forming a nitride film at the boundary with the metal film of the transition group, forming a high melting point silicide between the metal film of the transition group IVB group and the substrate to form a lower electrode, and forming a transition electrode VIII of the lower electrode. Forming a dielectric film on the group III metal film; and depositing a transition group VIII metal film on the dielectric film to form an upper electrode.

[0013]

The nitride film formed at the boundary between the transition group IVB metal film and the transition group VIII metal film acts as a diffusion barrier, and silicide plays a role in improving contact characteristics. In place of the transition group IVB group high melting point metal, a transition group VB group high melting point metal such as V, Nb, or Ta may be used. When depositing a high melting point metal film and a near noble metal film on silicon oxide, a nitride film is formed between the high melting point metal film and the near noble metal film to improve diffusion barrier characteristics, and A refractory metal oxide is formed between the silicon oxide film and the silicon oxide film to improve the adhesive strength with the silicon oxide film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming a capacitor electrode of a semiconductor device having a diffusion barrier function according to an embodiment of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B are diagrams illustrating an electrode forming process of a semiconductor device having a diffusion barrier function according to an embodiment of the present invention. Referring to FIG. 1A, a transition group IVB or VB group high melting point metal 12 is deposited on a silicon substrate 11, and a transition group VIII group noble metal 13 is deposited thereon. IVB of transition group such as Ti, Zr, Hf
Group metals or transition group VB metals such as V, Nb and Ta are refractory metals, and include Fe, Co, Ni, Ru, Rh, and P.
Transition group VIII metals such as d, Os, Ir, and Pt are near noble metals.

Referring to FIG. 1B, after the high melting point metal film 12 and the near noble metal film 13 are sequentially deposited on the substrate 11 as described above, a heat treatment process is performed in an ammonia NH ₃ atmosphere. In the present invention, unlike the conventional method, the process is performed in an NH ₃ atmosphere from the pre-purge stage. As a result of the heat treatment step, a nitride film 15 of the high melting point metal is formed at the boundary between the high melting point metal 12 and the near noble metal 13. At this time, the refractory metal film and the near noble metal film are each deposited to a thickness of 10 to 1000 °, and the heat treatment temperature is 5
00-1000 ° C. The near noble metal is a metal on which a nitride film is not well formed, and the high melting point metal is a metal on which a nitride film is well formed. Therefore, a boundary between the high melting point metal film 12 and the near noble metal film 13 is formed during a heat treatment process in an ammonia atmosphere. Nitrogen diffuses into the refractory metal 12 through the near-noble metal film 13 to form the refractory metal nitride film 15.

FIG. 3 is a graph showing the nitride formation energy and specific resistance of transition-group IVB, VB and VIB refractory metals. Here, the higher the melting point of the refractory metal, the greater the stability, and the smaller the specific resistance, the better the contact characteristics, that is, the electrical conductivity.

Referring to FIG. 3, the nitride forming energy of the refractory metals of the IVB and VB groups is large and stable, and the contact resistance is excellent since the specific resistance is low. Especially,
Ti, Zr, and Hf are excellent in stability and specific resistance characteristics. On the other hand, a group VIII near noble metal has a positive nitride formation energy, so that a nitride film is not formed well as described above. Then, the refractory metal film 12 and the substrate 11
After the heat treatment step, the high dielectric silicide 14 is formed by the reaction between the high dielectric metal and silicon. Since the high dielectric silicide 14 is formed at the boundary between the silicon substrate 11 and the high melting point metal film 12 to lower the contact resistance, the contact characteristics are improved. Therefore, when the process shown in FIG. 1 is used for the electrode forming process of the capacitor, the refractory metal film 12, the refractory metal nitride film 15 and the near noble metal film 13 are used.
Is used as the lower electrode of the capacitor.

When a lower electrode is formed by the above-described process, a pervoskit dielectric film is formed on the lower electrode by a normal process, and an upper electrode is formed thereon by a noble metal, chromium, or the like, a capacitor according to an embodiment of the present invention is obtained. An electrode is obtained.
At this time, since the high melting point metal silicide is formed at the boundary with the substrate and the contact resistance is reduced, the contact characteristics are improved, and the diffusion barrier characteristics and the electric conductivity are improved by the high melting point metal nitride film constituting the lower electrode. The characteristics are improved. In order to obtain the above characteristics, ammonia must be flowed into the apparatus from the pre-purge stage during the heat treatment process.

According to the present invention, N
The case where the heat treatment process is performed in the atmosphere of H ₃ and the case where the heat treatment process is performed in the atmosphere of N ₂ in the pre-purge stage as in the related art will be described in comparison. For example, Co and Zr are used as the refractory metal film 12 and the near noble metal film 13 on the substrate 11.
After each deposition, the case where the heat treatment process is performed in the N ₂ atmosphere from the pre-purge stage and the case where the heat treatment process is performed in the NH ₃ atmosphere from the pre-purge stage will be described with reference to FIGS. It is.

FIG. 5 shows Co / deposited on a silicon substrate.
FIG. 5A is an AES depth analysis diagram of the Zr double thin film. FIG. 5A is a heat treatment after deposition at 500 ° C. in an N ₂ atmosphere, and FIG. Depth analysis diagrams after heat treatment in an atmosphere of ° C. and N ₂ are shown. Referring to FIGS. 5B and 5C, after depositing Co / Zr on a silicon substrate, an atmosphere of 500 ° C. and N ₂ or 600 ° C. and N ₂
When the heat treatment process is performed in each atmosphere, mixing between the Co / Zr layers occurs.

However, as in the present invention, Co /
After depositing a double thin film of Zr, the pre-purge stage starts with NH
_{When a} heat treatment step is performed at 700 ° C. with the flow of ₃ , nitrogen is diffused through the upper noble metal film 13 and reacts with Zr of the lower refractory metal film 12 as shown in FIG. Therefore, it can be seen that the surface of the refractory metal film 12 reacts with nitrogen to become the refractory metal nitride film 15 and the refractory metal silicide 14 is formed at the boundary between the silicon substrate 11 and the refractory metal film 12. In the conventional method, inter-layer mixing occurs even during the heat treatment at 500 ° C., but in the present invention, inter-layer mixing does not occur at all even when the heat treatment is performed at a heat treatment temperature of 700 ° C., which is higher than before.

FIGS. 2A and 2B are views showing a process of forming an electrode of a semiconductor device having a diffusion barrier function according to another embodiment of the present invention. Referring to FIG. 2A, the silicon substrate 1
2, a silicon oxide film 22 is formed on
A group VIII or VB group metal film 23 is deposited, and a transition group VIII group metal film 24 is deposited thereon. Again,
A transition group IVB group metal such as Ti, Zi, and Hf or a transition group VB group metal film 23 such as V, Nb, and Ta is a high melting point metal, and includes Fe, Co, Ni, Ru, Rh, Pd,
The transition group VIII group metal film 24 such as Os, Ir, and Pt is a near noble metal.

Referring to FIG. 2B, after the high melting point metal film 23 and the near noble metal film 24 are deposited as described above, a heat treatment process is performed in an ammonia NH ₃ atmosphere. During the heat treatment process, ammonia flows into the apparatus from the pre-purge stage. As a result of the heat treatment process, nitrogen diffuses through the near-noble metal film 24 at the boundary between the high-melting point metal film 23 and the near-noble metal film 24 and reacts with the high-melting point metal. A nitride film 26 is formed. Refractory metal nitride film 2
No. 6 not only has excellent conductivity, but also has excellent properties as a diffusion barrier. At this time, since the near-noble metal film 24 is not a metal that easily reacts with nitrogen to become a nitride film, nitrogen diffuses through the near-noble metal film 24 and reacts with the high melting point metal film. At the boundary between the refractory metal film 23 and the silicon oxide film 22, the refractory metal and the silicon oxide film react to form a refractory metal oxide film 25.

FIG. 4 is a graph showing the oxide formation energy and the solubility of oxygen of the refractory metals belonging to the groups IVB, VB and VIB. Referring to FIG. 4, since the oxide films of the IVB group and the VB group are more stable than the silicon oxide film, they are reduced by the refractory metal to form the refractory metal oxide film 25,
This refractory metal oxide film 25 has excellent adhesion to the silicon oxide film 22. Since the oxide formation energy (absolute value) of the near noble metal is smaller than that of the silicon oxide film, the near noble metal 24 is not excellent in the adhesive force with the silicon oxide. Therefore, when only the near noble metal is used as the electrode, there is a disadvantage that the adhesive force with the silicon oxide film is not excellent, but the high melting point metal film 23 as in the present invention is replaced with the near noble metal film 24.
By performing a heat treatment step after forming the metal oxide film 25 at a lower portion, the high-melting-point metal oxide film 25 can be formed to improve the adhesive strength between the boundaries.

FIG. 7 shows an AES depth analysis diagram of a Co / Zr double thin film after a Co / Zr double thin film is deposited on a silicon oxide film and heat-treated. FIG. 7 (A) shows 600 ° C., N
₂ atmosphere, FIG. 7 (B) 600 ° C., a case of performing each heat treatment step in an atmosphere of NH _3, at the time of the heat treatment step in N ₂ atmosphere mixing between Likewise Co / Zr film as in FIG. 5 Co / Zr during the heat treatment process in an NH ₃ atmosphere.
ZrN is formed at the boundary of and acts as a diffusion barrier,
ZrSi _x O _Y is formed at the boundary with the silicon oxide film to improve the adhesive strength with the silicon oxide film.

After the heat treatment step, the refractory metal film 23, refractory metal nitride film 26 and near noble metal film 24 formed on the silicon oxide film function as lower electrodes of the capacitor electrodes. Therefore, the near noble metal film 24 constituting the lower electrode
When a Perboss Kit dielectric film is formed thereon and a near noble metal film such as platinum is formed as an upper electrode, a capacitor electrode is obtained. The Co / Zr of the present invention shown in FIGS.
The characteristics of the double thin film are not limited to the Co / Zr double thin film,
The present invention can be applied to all of the near-noble metal / high melting point metal double thin films.

[0027]

According to the present invention described above, the near noble metal film /
By depositing a double thin film of a high melting point metal film on a silicon substrate and then performing heat treatment in an atmosphere of ammonia from a pre-purge step, an electrode having an excellent diffusion barrier function and good contact characteristics can be formed. . Furthermore, by depositing a double thin film of a near noble metal film / a high melting point metal film on a silicon oxide film and then performing a heat treatment in an atmosphere of ammonia from the pre-purge stage, it has an excellent diffusion barrier function and excellent adhesive strength. Electrodes can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an electrode forming process of a semiconductor device having a diffusion barrier function according to an embodiment of the present invention.

FIG. 2 is a process diagram of forming an electrode of a semiconductor device having a diffusion barrier function according to another embodiment of the present invention;

FIG. 3 is a graph showing nitride formation energy and specific resistance of transition-group IVB, VB, and VIB-group refractory metals.

FIG. 4 is a graph showing oxide film formation energies of transition group IVB, VB, and VIB group refractory metals.

5A and 5B are AES depth analysis diagrams of a Co / Zr double thin film, wherein FIG. 5A is a depth analysis diagram after deposition, and FIG.
Depth analysis after heat treatment in N ₂ atmosphere, (C) shows 6
FIG. 5 is a depth analysis diagram after heat treatment in an atmosphere of N ₂ at 00 ° C.

FIG. 6 shows a pre-purgation of a Co / Zr double thin film.
FIG. 7B is a depth analysis diagram of AES after heat treatment at 700 ° C. in a state where NH ₃ flows from the stage e).

FIG. 7 is a depth analysis diagram of AES after heat treatment of a Co / Zr double thin film deposited on a SiO ₂ substrate at 600 ° C. FIG. 7A shows a depth analysis after heat treatment in an N ₂ atmosphere. FIG. 3B is a depth analysis diagram after heat treatment in an NH ₃ atmosphere.

FIG. 8 is a flowchart showing a heat treatment process for forming the electrodes of FIGS. 1 and 2;

FIG. 9 is a structural diagram of a capacitor electrode using a conventional Perboss kit dielectric.

[Explanation of symbols]

11, 21: silicon substrate, 12, 23: refractory metal,
12, 24: near noble metal, 14: refractory metal silicide,
15, 26: high melting point metal nitride film, 22: silicon oxide film, 25: high melting point metal oxide film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H01L 27/04

Claims (9)

(57) [Claims] A step of sequentially depositing a transition group IVB metal film and a transition group VIII metal film on a silicon substrate; and performing a heat treatment process in an ammonia atmosphere to form the transition group IVB metal film.
Forming a nitride film on a boundary between the group III metal film and the transition group metal group VIII, forming silicide between the transition group IVB metal film and the substrate to form a lower electrode; Forming a dielectric film on a transition group VIII metal film of the lower electrode; and depositing a transition group VIII metal film on the dielectric film to form an upper electrode. A method for forming an electrode of a semiconductor device having a diffusion barrier function, characterized by comprising: 2. The semiconductor device having a diffusion barrier function according to claim 1, wherein the transition group IVB metal film and the transition group VIII metal film are each deposited to a thickness of 10 to 1000 °. Electrode forming method. 3. The method according to claim 1, wherein the heat treatment is performed at a temperature of 500 to 1000 ° C. 4. The transition group IVB group metal, Ti,
2. The method for forming an electrode of a semiconductor device having a diffusion barrier function according to claim 1, wherein one of refractory metals such as Zr and Hf is used. 5. The transition group VIII metal, Fe,
2. The method according to claim 1, wherein one of near noble metals such as Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt is used. 6. The method for forming an electrode of a semiconductor device having a diffusion barrier function according to claim 1, wherein a transition group VB group metal is used instead of the transition group IVB group metal. 7. V, N are selected from the group VB metals of the transition group.
7. The method for forming an electrode of a semiconductor element according to claim 6, wherein one of near noble metals such as b and Ta is used. 8. Prior to depositing a transition group IVB metal,
2. The method of claim 1, further comprising depositing a silicon oxide film. 9. A refractory metal oxide film is formed at a boundary between the silicon oxide film and the transition group IVB metal film by reduction of the transition group IVB metal after the heat treatment step. A method for forming an electrode of a semiconductor device having the diffusion barrier function described above.