CN110911352B

CN110911352B - A kind of diffusion barrier layer for Cu interconnect and its preparation method and application

Info

Publication number: CN110911352B
Application number: CN201911229887.0A
Authority: CN
Inventors: 孟瑜; 宋忠孝; 李雁淮
Original assignee: Xian University
Current assignee: Xian University
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2022-05-17
Anticipated expiration: 2039-12-04
Also published as: CN110911352A

Abstract

The invention discloses a diffusion barrier layer for Cu interconnection, a preparation method and application thereof. By doping Ru atoms with different contents in ZrB ₂ thin films, the crystal structure of the thin films is changed, the fast diffusion channels of Cu atoms are eliminated, and the fast diffusion channels of Cu atoms are eliminated. The diffusion path is extended, and the high temperature stability performance of the diffusion barrier layer is improved. In addition, metal Ru has a low resistivity and exists in the form of elemental metal in the diffusion barrier layer, which can improve the electrical conductivity of Zr‑Ru‑B. Compared with Zr atoms, Ru atoms are not easily oxidized, thus reducing O Doping of elements, through high-temperature annealing treatment, a large number of holes appear on the surface of the Cu film, forming a copper-silicon high-resistance phase, and the scattering of electrons on the surface of the sample is enhanced, and the obtained Zr-Ru-B ternary structure has good high temperature stability. Therefore, the diffusion barrier performance of the diffusion barrier layer is improved, and the reliability of the Cu interconnection line is further improved, thereby increasing the life of the integrated circuit.

Description

Diffusion barrier layer for Cu interconnection and preparation method and application thereof

Technical Field

The invention belongs to the technical field of super-large-scale integrated circuit manufacturing, and particularly relates to a diffusion barrier layer for Cu interconnection and a preparation method thereof.

Background

The Cu metal wire has lower resistivity, high temperature stability, high thermal conductivity and excellent electromigration resistance, so that the Cu metal wire is a mainstream interconnection material instead of the traditional Al lead wire. Although Cu lines are the most promising interconnect leads for very large scale integrated circuits, they have their own shortcomings: firstly, the Cu can react with Si or a low-k dielectric layer at the temperature lower than 200 ℃ to generate high-resistance copper-silicon phase Cu₃Si, which leads to an increase in the resistance of the entire interconnect system and can damage the interconnect system, which ultimately leads to device failure, and Cu can diffuse into Si rapidly (diffusion coefficient D)_Cu＝4.7×10^- ³cm²·s^-1) Causing deep well defects and reducing minority carrier lifetime; secondly, the bonding performance of Cu and a Si substrate is poor, the peeling between a film layer and the substrate is easy to occur, and the defects obviously limit the application of the Cu interconnection line in the ultra-large scale integrated circuit.

The best solution is to use Cu and Si or SiO₂Between the layers is added a Diffusion Barrier (DB), referred to as Diffusion Barrier (Barrier), which on the one hand prevents Cu from diffusing into Si or SiO₂One in the otherThe aspect can enhance the bonding strength between Cu and the dielectric layer. In addition to Cu interconnects, diffusion barriers have also found application in chip packaging. Therefore, the problems of selecting materials for the diffusion barrier layer material and how to select the optimal preparation process become hot spots for research.

Among the alternatives for the diffusion barrier, borides have very excellent physical properties, such as low resistivity, high melting point, good chemical stability, and excellent mechanical properties. In particular a binary compound ZrB₂Inherently having a lower resistivity (4.6 μ Ω. cm) and a higher melting point (3245 ℃ C.). In addition, ZrB₂Can be epitaxially grown on Si (111), 4H-SiC (0001), GaN (0001) and Si (001) substrates, has small lattice mismatch, is favorable for structural stability and inhibits atoms from being in ZrB₂Medium high temperature diffusion. Wang P et al deposited ZrB on graphene substrates using CVD techniques₂The results show that ZrB was produced₂The structure is a polycrystalline structure, and the internal structure is loose. This provides a rapid diffusion path for Cu atoms, and the barrier effect is poor, and in addition, the structural porosity increases the resistivity.

Disclosure of Invention

The invention aims to provide a diffusion impervious layer for Cu interconnection and a preparation method thereof, which overcome the defects of the existing method.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a diffusion impervious layer for Cu interconnection comprises the following steps:

step 1), performing decontamination treatment on the surface of a silicon substrate;

step 2), co-sputtering Ru target and ZrB on the surface of the silicon substrate subjected to decontamination treatment by magnetron sputtering₂The sputtering power of the Ru target is 20-50W and ZrB₂The sputtering power of the target is 100-150W; the co-sputtering time is 1200-1800 s, and the Zr-Ru-B diffusion impervious layer film is obtained.

Further, the magnetron sputtering in the step 2) is carried out in a vacuum inert gas atmosphere.

Furthermore, Ne gas or Ar gas is used as the inert gas, the flow rate of the inert gas is 20-30 sccm, and the working pressure is 0.3-0.5 Pa.

Further, the background vacuum degree of the sputtering chamber for magnetron sputtering is 1.0 multiplied by 10^-4～6.0×10^-4Pa。

Further, Ru target and ZrB₂The purity of the target material is 99.99 percent.

Further, the Ru target material adopts radio frequency magnetron sputtering, ZrB₂The target material adopts direct current magnetron sputtering.

The thickness of the diffusion impervious layer film for Cu interconnection is 3-10 nm.

A preparation method of a Cu interconnection lead layer based on a diffusion impervious layer for Cu interconnection comprises the following steps:

step 1), preparing and forming a Zr-Ru-B diffusion impervious layer on the surface of a silicon substrate;

and 2) carrying out magnetron sputtering of a Cu target on the Zr-Ru-B diffusion barrier layer to form a Cu lead layer, and then carrying out high-temperature annealing to obtain a Cu interconnection lead layer containing the Zr-Ru-B diffusion barrier layer, wherein the annealing temperature is 300-700 ℃, and the heat preservation time is 30-60 min.

Further, the Cu target is deposited by direct current sputtering, the magnetron sputtering deposition power is 100-130W, and the deposition pressure is 0.2-0.5 Pa.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention provides a preparation method of a diffusion impervious layer for Cu interconnection, which is characterized in that ZrB is adopted₂The film is doped with Ru atoms, so that the crystal structure of the film is changed, a rapid diffusion channel of Cu atoms is eliminated, a diffusion path is prolonged, and the high-temperature stability of the diffusion barrier layer is improved.

A Cu interconnection lead layer based on diffusion impervious layer for Cu interconnection is prepared through preparing ZrB₂The Ru atoms are doped into the thin film, so that the crystal structure of the thin film is changed, a rapid diffusion channel of Cu atoms is eliminated, a diffusion path is prolonged, the high-temperature stability of the diffusion barrier layer is improved, the metal Ru has lower resistivity, and exists in the diffusion barrier layer in a simple substance metal form, so that the conductivity of Zr-Ru-B can be improved, and compared with the Zr atoms, the Ru atoms are not easy to oxidize, so that the doping of O elements is reduced; by high temperature annealing treatment, CAnd a large number of holes appear on the surface of the u film to generate a copper-silicon high-resistance phase, the scattering effect of the surface of the sample on electrons is enhanced, the obtained Zr-Ru-B ternary structure has better high-temperature stability, the diffusion barrier property of the diffusion barrier layer is improved, and the reliability of the Cu interconnection line is further improved.

Drawings

FIG. 1 is an HRTEM image of the amorphous structure of a diffusion barrier with 5.39% Ru content.

Fig. 2 is an HRTEM of an amorphous structure of a diffusion barrier with 52.41% Ru content.

FIG. 3 is an SEM image of a film system with 5.39% Ru content after annealing at 650 ℃.

FIG. 4 is an XRD pattern of a Cu/Zr-Ru-B thin film with a Ru content of 8.99%.

FIG. 5 is a plot of sheet resistance of a Cu/Zr-Ru-B film with a Ru content of 37.14%.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

step 1), performing decontamination treatment on the surface of a silicon substrate; specifically, a silicon substrate is sequentially placed in acetone and ethanol for ultrasonic cleaning to remove organic pollutants on the surface of the silicon substrate and improve the film-substrate binding force; wherein the concentration of the acetone solution is more than 99.9 percent; the concentration of the ethanol solution is more than 99.9 percent.

The magnetron sputtering in the step 2) is carried out in a vacuum inert gas atmosphere.

The background vacuum degree of a sputtering chamber for magnetron sputtering is 1.0 multiplied by 10^-4～6.0×10^-4Pa; ru target material adopts radio frequency magnetron sputtering, ZrB₂The target material adopts direct current magnetron sputtering. The method is implemented at normal temperature by adopting double-chamber magnetron sputtering coating equipment; ru target and ZrB used therefor₂The purity of the target material is 99.99 percent; the Ru target material adopts radio frequency magnetron sputtering, ZrB₂The target material adopts direct current magnetron sputtering. The prepared Zr-Ru-B diffusion impervious layer is an alloy diffusion impervious layer.

Ne gas or Ar gas is used as the inert gas, the flow rate of the inert gas is 20-30 sccm, and the working pressure is 0.3-0.5 Pa.

The invention provides a diffusion impervious layer for Cu interconnection, wherein a doped Ru element exists in a metal form, and the thickness of an obtained Zr-Ru-B diffusion impervious layer film is 3-10 nm.

A preparation method of a Cu interconnection lead layer based on the diffusion impervious layer for Cu interconnection comprises the following steps:

step 2), forming a Cu lead layer on the Zr-Ru-B diffusion barrier layer through magnetron sputtering of a Cu target, and then performing high-temperature annealing to obtain a Cu interconnection lead layer containing the Zr-Ru-B diffusion barrier layer, wherein the annealing temperature is 300-700 ℃, and the heat preservation time is 30-60 min; the magnetron sputtering deposition power is 100-130W, and the deposition pressure is 0.2-0.5 Pa.

Examples

Adopts JPG-450a type double-chamber magnetron sputtering equipment to sputter Zr-Ru-B diffusion impervious layer film, and the target materials are Ru target and ZrB₂Target, argon gas with purity of 99.99%, Ru target and ZrB₂Sputtering power of the target is respectively 30W and 120W, bias voltage is 150V, working pressure is 0.3Pa, pre-sputtering time is 15min, and sputtering time is 0.5h, so that a diffusion barrier layer film with the thickness of 5nm is obtained; after the deposition of the diffusion barrier layer film is finished, depositing a 200nm Cu film by using direct current sputtering, wherein the purity of a Cu target is 99.99%, the magnetron sputtering deposition power is 120W, and the deposition pressure is 0.3 Pa; obtaining a Cu interconnection sample containing a Zr-Ru-B diffusion barrier layer, carrying out high-temperature annealing on the prepared Cu interconnection sample in an atmosphere annealing furnace, wherein the annealing temperature is 300-700 ℃, the heat preservation time is 30-60min, and then testing the Cu interconnection sample containing the Zr-Ru-B diffusion barrier layer;

the diffusion barrier layer film is prepared under the condition of different magnetron sputtering powers, and the specific parameters are shown in table 1:

TABLE 1

When the microstructure of the Zr-Ru-B diffusion barrier layer prepared in the above embodiment is observed by TEM, as can be seen from fig. 1 and fig. 2, when the Ru doping content is low, the film is in an amorphous structure, and when the Ru doping content is high, the film is in a nanocrystalline structure; FIG. 3 is an SEM picture of a film system with 5.39% Ru content after annealing at 650 ℃, which shows that the surface of the Cu film is aggregated and has a large number of holes and a small number of rod-shaped particles are generated, and the particles are Cu-Si compounds through energy spectrum analysis, which shows that diffusion has occurred inside the film and the diffusion barrier layer fails. FIG. 4 is an XRD pattern of a Cu/Zr-Ru-B film with 8.99% Ru content, and no diffraction peak associated with Cu-Si compounds was observed after annealing the sample to 700 deg.C, indicating that the film system did not fail at least at 700 deg.C.

And (3) measuring the square resistance values of the film in a deposition state and an annealing state by adopting a four-point probe tester for the film sample of the diffusion barrier layer, preparing the film sample of the diffusion barrier layer into a square block of 1cm multiplied by 1cm before testing, testing each sample for 5 times to ensure the accuracy of the test, and finally obtaining the square resistance of the film by taking an average value. As shown in fig. 5, when annealing is performed at 500 ℃ or lower, the sheet resistivity decreases with the increase in annealing temperature, which is caused by the decrease in the number of defects in the Cu film and the disappearance of internal stress. After annealing at 600 ℃ and 700 ℃, the square resistance of the sample is increased sharply, a large number of holes appear on the surface of the Cu film, a copper-silicon high-resistance phase is generated, and the scattering effect of the surface of the sample on electrons is enhanced. In conclusion, compared with the nanocrystalline structure, the amorphous structure has higher thermal stability and better blocking effect on Cu and Si atom diffusion at high temperature.

Claims

1. a preparation method of Cu interconnection diffusion barrier layer, is characterized in that, comprises the following steps:

Step 1), decontamination treatment on the surface of the silicon substrate;

Step 2), co-sputtering Ru target and ZrB ₂ target on the surface of the decontaminated silicon substrate by magnetron sputtering, the Ru target sputtering power is 20-50W, and the ZrB ₂ target sputtering power is 100-150W; co-sputtering time is 1200-1800s to obtain Zr-Ru-B diffusion barrier film; magnetron sputtering is carried out under vacuum inert gas atmosphere; inert gas is Ne gas or Ar gas, and the inert gas flow rate is 20 ～30sccm, the working pressure is 0.3～0.5Pa; the background vacuum degree of the sputtering chamber of magnetron sputtering is 1.0×10 ^-4 ～6.0×10 ^-4 Pa.

2 . The method for preparing a diffusion barrier layer for Cu interconnection according to claim 1 , wherein the purity of the Ru target material and the ZrB ₂ target material are both 99.99%. 3 .

3 . The method for preparing a diffusion barrier for Cu interconnection according to claim 1 , wherein the Ru target material adopts radio frequency magnetron sputtering, and the ZrB ₂ target material adopts DC magnetron sputtering. 4 .

4 . A diffusion barrier layer for Cu interconnection, characterized in that it is prepared by any one of the above claims 1 to 3 . 5 .

5 . The diffusion barrier layer for Cu interconnection according to claim 4 , wherein the thin film thickness of the diffusion barrier layer for Cu interconnection is 3 to 10 nm. 6 .

6. a Cu interconnection lead layer preparation method based on Cu interconnection diffusion barrier layer, is characterized in that, comprises the following steps:

Step 1), preparing and forming a Zr-Ru-B diffusion barrier layer on the surface of the silicon substrate;

Step 2), magnetron sputtering a Cu target on the Zr-Ru-B diffusion barrier layer to form a Cu lead layer, and then performing high temperature annealing to obtain a Cu interconnection lead layer containing the Zr-Ru-B diffusion barrier layer, and the annealing temperature is 300 ℃ ～700℃, the holding time is 30-60min.

7. The method for preparing a Cu interconnection lead layer based on a diffusion barrier layer for Cu interconnection according to claim 6, wherein the Cu target is deposited by DC sputtering, and the magnetron sputtering deposition power is 100-130W, The deposition pressure is 0.2～0.5Pa.