JP2751864B2 - Oxygen diffusion barrier electrode and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode structure formed on a semiconductor surface and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, when an oxide dielectric such as a ferroelectric is to be incorporated as a capacitor into a semiconductor integrated circuit, a temperature of 500 ° C. which is required when many oxide dielectrics are manufactured.
There has been a problem that the polycrystalline silicon used as the lower electrode for the capacitor is oxidized due to the high temperature and the oxidizing atmosphere, and a contact failure occurs. Therefore, in many cases, a high melting point noble metal such as Pt having high heat resistance and oxidation resistance is used as the lower electrode as shown in FIG. That is, a silicon barrier layer 2 of TiN or the like under the high melting point noble metal layer 1
Is used as an electrode that prevents silicidation of the high melting point noble metal and can withstand oxide dielectric production. Since the conductive oxide electrode is also stable to an oxidizing atmosphere, it has been studied to use the conductive oxide electrode by providing a silicon barrier layer thereunder to prevent silicidation.

[0003]

However, the conventional lower electrode structure has the following problems. When a high melting point noble metal such as Pt is used, oxygen can pass through the crystal grain boundaries of the high melting point metal thin film, and TiN used as a silicon barrier layer under the high melting point noble metal during oxide dielectric fabrication. Is oxidized to form an insulative titanium oxide, resulting in poor conduction with the silicon substrate. Also, when a conductive oxide is used, TiN is oxidized at the time of forming the conductive oxide on the TiN of the silicon barrier, so that a conduction failure occurs and the problem is not solved.

[0004] It is an object of the present invention to provide an electrode structure that can solve the above problems.

[0005]

According to the present invention, there is provided an electrode for making electrical contact with a semiconductor surface, wherein a columnar crystal grain of a polycrystalline high melting point noble metal layer laminated on a semiconductor diffusion barrier layer formed on the semiconductor surface is provided. An oxygen diffusion barrier electrode comprising an oxygen diffusion barrier portion provided in the field. Here, the oxygen diffusion barrier portion is preferably made of a metal oxide of one or a combination of Ti, Zr, Ta, and Ru. Further, in the method of manufacturing an oxidation diffusion barrier electrode, a semiconductor diffusion barrier layer is formed on a semiconductor surface, and Ti, Zr, Ta, and Ru are formed on the semiconductor diffusion barrier layer.
Forming a polycrystalline high-melting-point noble metal layer composed of columnar crystals with a metal layer of any one or a combination of a plurality of types interposed therebetween, and then performing a heat treatment at 450 to 650 ° C. in a non-oxidizing atmosphere. And Here, the method may further include a step of removing the barrier metal deposited on the refractory metal layer.

[0006]

The electrode structure according to the present invention uses Pt as a refractory metal.
1 is shown in FIG. When Pt is produced by a sputtering method or the like, a polycrystalline film is formed and the crystal grains have a columnar structure unless a special substrate is selected. When an oxide dielectric is formed on Pt, oxygen diffuses through the columnar Pt crystal grain boundaries and oxidizes a silicon barrier such as TiN under Pt to cause a contact failure. In this way, oxygen diffusion acts as a trap for oxygen before being oxidized to the grain boundary because the grain boundary is the main path, and oxygen acts as a barrier to oxygen diffusion after being oxidized. If a metal having a barrier property, for example, Ti is arranged, diffusion of oxygen at the grain boundary can be suppressed, and as a result, oxidation of TiN can be suppressed. Also P
Since the crystal grain boundary of t is formed perpendicular to the substrate surface, an oxide of a metal having an oxygen barrier property exists in this portion, and the oxide does not increase the contact resistance even if the oxide is insulative. , A metal that becomes an electrically conductive oxide, for example, Ru, and a metal that becomes an insulating oxide, for example, Zr, Ta
Etc. can be used.

[0007]

【Example】

(Example 1) FIG. 2 shows the results of composition analysis in the depth direction at each stage of the fabrication of a lower electrode and a capacitor when using Pt as a high melting point noble metal and Ti as an oxygen barrier metal. FIG. 2A shows, from the substrate side, polycrystalline silicon, a TiN / Ti laminated silicon barrier layer, a 20 nm thick Ti oxygen diffusion barrier layer, and a 200 nm Pt layer. When the structure of FIG. 2A was heat-treated for 30 minutes in nitrogen at 500 ° C., as shown in FIG.
It diffused in the t layer and on the Pt surface. At this time, when the cross section of the sample was observed with a high-resolution electron microscope, it was observed that the diffused Ti was precipitated on the surface of Pt and crystal grain boundaries. Pt
After the Ti deposited on the surface was removed by etching, lead zirconate titanate (PZT) was produced as an oxide dielectric by heat treatment at 600 ° C. for 60 minutes by a sol-gel method. FIG. 2 (c) shows the result of the composition analysis after PZT fabrication, and it was found that Ti present at the Pt grain boundary was oxidized near the Pt surface, but Ti at the Pt grain boundary on the TiN side was oxidized. And the TiN layer was not oxidized. This electrode structure is 10 μm × 10 μm by ion milling.
When the contact resistance was measured after microfabrication,
It was 50Ω, and it was confirmed that there was no problem in conduction as the lower electrode. The required Pt film thickness depends on the heat treatment time and temperature in an oxidizing atmosphere, but if the heat treatment is performed at a temperature of 600 ° C. or less and 60 minutes or less, 150 nm or more is desirable, and when it is 150 nm or less, the contact resistance tends to increase. .

(Embodiment 2) A case where Ir is used as a high melting point noble metal and Ti is used as an oxygen barrier metal will be described. The manufacturing method is the same as that of the first embodiment.
TiN / Ti laminated silicon barrier layer, 20 nm thick Ti
After forming an oxygen diffusion barrier layer, also an Ir layer of 200 nm, this structure is heat-treated at 650 ° C. for 30 minutes in nitrogen, so that the Ti layer under Ir diffuses the Ir grain boundary, and the Ir grain boundary and the Ir surface. Was precipitated. After the Ti deposited on the Ir surface is removed by etching, lead zirconate titanate (PZT) is formed as an oxide dielectric by a sol-gel method at 600 ° C.
The part from which ZT was removed was 10 μm thick by ion milling.
When the contact resistance was measured after fine processing to a size of × 10 μm, it was 50 to 100Ω, and it was confirmed that there was no problem in conduction as the lower electrode. In case of Ir electrode, Ir surface is 6
Although oxidized in oxygen at 00 ° C., IrO ₂ was a conductive oxide and did not hinder the conductivity of the electrode. In the case of the Ir electrode, the temperature required for the grain boundary diffusion of the oxygen barrier metal was higher by about 100 to 150 ° C. than in the case of using the Pt electrode.

Table 1 shows the contact resistance of each combination using a Pt or Ir electrode and various oxygen barrier metals. The contact resistance value of each element of Zr, Ta, and Ru was a value having no problem when used as a lower electrode.

[0010]

[Table 1]

[0011]

According to the present invention, in a polycrystalline high melting point noble metal which makes electrical contact from the surface of a semiconductor, an oxygen diffusion barrier portion is provided at a grain boundary of a columnar crystal of the polycrystalline high melting point noble metal, and the semiconductor is interposed through the crystal grain boundary. By preventing the diffusion of oxygen that diffuses between the surface and the high-melting noble metal electrode and ensuring electrical continuity in the crystal parts other than the crystal grain boundaries, a highly conductive polycrystalline high-melting noble metal electrode is formed on the semiconductor surface. realizable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a lower electrode structure in which an oxygen barrier metal is disposed at a high melting point noble metal grain boundary according to the present invention.

FIG. 2 is a result of a composition analysis in a depth direction at each stage when a lower electrode and a capacitor are manufactured when Pt is used as a high melting point noble metal and Ti is used as an oxygen barrier metal.

FIG. 3 is a diagram showing a lower electrode structure in the case where a conventional oxygen barrier metal is not used.

[Explanation of symbols]

 Reference Signs List 1 Pt lower electrode (high melting point noble metal layer) 2 TiN / Ti laminated silicon barrier layer 3 Polycrystalline silicon 4 Ti (oxygen barrier metal)

Claims (4)

(57) [Claims] In an electrode which makes electrical contact with a semiconductor surface, an oxygen diffusion barrier portion is formed at a crystal grain boundary of a columnar crystal of a polycrystalline high melting point noble metal layer laminated on a semiconductor diffusion barrier layer provided on the semiconductor surface. An oxygen diffusion barrier electrode comprising: 2. An oxygen diffusion barrier section comprising Ti, Zr, Ta, R
2. The oxygen diffusion barrier electrode according to claim 1, comprising an oxide of a metal obtained by combining one or more of u. 3. A semiconductor diffusion barrier layer is formed on a semiconductor surface, and Ti, Zr, Ta, and Ru are formed on the semiconductor diffusion barrier layer.
Forming a polycrystalline high-melting-point noble metal layer composed of columnar crystals with a metal layer of any one or a combination of a plurality of types interposed therebetween, and then performing a heat treatment at 450 to 650 ° C. in a non-oxidizing atmosphere. Claim 1 or 2
A method for producing the oxygen diffusion barrier electrode according to the above. 4. The oxygen diffusion barrier according to claim 3, further comprising a step of removing the barrier metal deposited on the refractory metal layer after heat treatment at 450 to 650 ° C. in a non-oxidizing atmosphere. Method for producing a conductive electrode.