CN113957385A

CN113957385A - NbTaMoWN with high-temperature diffusion shielding performancexNitride coating and method for producing the same

Info

Publication number: CN113957385A
Application number: CN202111220986.XA
Authority: CN
Inventors: 王闻晓; 江依诺; 刘睿; 李建亮; 李航
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2021-10-20
Filing date: 2021-10-20
Publication date: 2022-01-21

Abstract

The invention discloses NbTaMoWN with high-temperature diffusion shielding performance_xNitride coatings and methods of making the same. The method takes NbTaMoW high-entropy alloy as a magnetron sputtering target material, adopts a direct-current magnetron sputtering method, and adopts a method of forming a layer of metal on Ar and N₂Under the atmosphere, NbTaMoWN with high-temperature diffusion shielding performance is prepared_xAnd (3) nitride coating. The invention prepares NbTaMoWN by a direct-current magnetron sputtering method_xThe nitride coating has simple and rapid process and good repeatability, and the prepared NbTaMoWN_xThe nitride coating is in an amorphous phase structure, has small thickness, good thermal stability, electrical property and high-temperature diffusion shielding property, and can be applied to integrated circuitsAs a diffusion barrier in Cu-Si devices.

Description

NbTaMoWN with high-temperature diffusion shielding performancexNitride coating and method for producing the same

Technical Field

The invention belongs to the technical field of microelectronic materials, and relates to a preparation method of a silicon nitride/silicon nitride composite materialNbTaMoWN with high-temperature diffusion shielding performance_xNitride coatings and methods of making the same.

Background

Cu has low resistivity, high electromigration resistance and relatively low cost, and is widely used in high-speed ultra-large scale integrated circuit. However, Cu is easily moved in a temperature-rising environment and is mixed with Si/SiO₂Formation of orthogonal eta-Cu₃A Si compound. The formation of silicide consumes Si and increases the volume of the material, resulting in breakdown of the surface discharge region, causing a change in the electrical properties of Cu. Therefore, a barrier coating for suppressing diffusion between the Si and Cu conductive layers is required (mostly applied in the high temperature environment of 600-900 ℃). At present, more coating materials mainly comprise Ta, Ti, TaN, CrN, TiAlN and the like. However, these materials often have a polycrystalline structure inside, which is easy to provide a grain boundary channel for Cu atom diffusion, and the diffusion shielding performance is not ideal, and cannot meet the performance requirements.

In recent years, researches find that the high-entropy alloy has better mechanical property, wear resistance and corrosion resistance, has a high-entropy effect, a lattice distortion effect and a delayed diffusion effect, is easy to form an amorphous structure, is difficult to diffuse atoms in the amorphous structure, and still has higher diffusion shielding capability even if the thickness of the high-entropy alloy is lower than that of other types of coating systems, so that the high-entropy alloy is paid much attention as a research object of a Cu interconnection diffusion barrier layer.

Preparation of FeCrVTa by Wangzoxin and the like by adopting radio frequency magnetron sputtering method_0.4W_0.4N_xCoating, found with increasing N content in the coating (N)₂Flow ratio less than 10%), hardness and Young's modulus increase, but at the same time the sheet resistance also increases. Lirong et al prepared AlCrTaTiZrMoN by DC magnetron reactive sputtering_xCoating, found with increasing N content (N)₂Flow rate ratio less than 10%), the thermal stability of the coating is improved, but the sheet resistance thereof is also increased. The documents show that the mechanical property of the coating is improved but the electrical property of the coating is reduced by adding the N element into the high-entropy alloy coating along with the increase of the N content, so that the N content in the coating needs to be reasonably controlled to balance and adjust the mechanical property and the electrical property of the coatingAnd (4) performance.

Disclosure of Invention

The invention aims to provide NbTaMoWN with high-temperature diffusion shielding performance_xNitride coatings and methods of making the same. The NbTaMoWN_xThe nitride coating has better diffusion shielding performance, better thermal stability and lower resistivity.

The technical scheme for realizing the purpose of the invention is as follows:

NbTaMoWN with high-temperature diffusion shielding performance_xThe preparation method of the nitride coating comprises the following steps: by means of DC magnetron sputtering, in N₂5% by weight of Ar and N₂Under the mixed atmosphere, taking NbTaMoW high-entropy alloy as a target material, and sputtering on a Si single polishing piece to obtain NbTaMoWN_xAnd (3) nitride coating.

Preferably, the conditions of the dc magnetron sputtering method are as follows: the target base distance is 7-10 cm, the vacuum degree of the back bottom is lower than 4.3 multiplied by 10^-3Pa, working pressure of 0.2-0.4 Pa, total gas flow of 40sccm, Ar flow of 37-39 sccm, and N₂The flow rate is 1-3 sccm, the sputtering power is 90-110W, and the sputtering time is 6-10 min.

The NbTaMoWN with high-temperature diffusion shielding performance_xThe nitride coating is of an amorphous phase structure, the range (x) of the ratio of N atoms to the sum of Nb, Ta, Mo and W atoms is 0.1-0.15, and the thickness of the coating is 100-200 nm.

Preferably, x is 0.13.

Compared with the prior art, the invention has the following advantages:

(1) NbTaMoWN prepared by the invention_xThe nitride coating is of an amorphous phase structure, N elements are doped on the basis of the NbTaMoW high-entropy alloy coating, and the content of N is controlled, so that an atom diffusion channel is further reduced, the atom diffusion difficulty is higher, the generation of a Cu-Si compound is effectively inhibited, and the nitride coating has better diffusion shielding performance.

(2) NbTaMoWN prepared by the invention_xThe nitride coating has compact surface, no crack, cavity and other defects at high annealing temperature (less than or equal to 800 ℃), and good thermal stabilityAnd (4) sex.

(3) The preparation process of the invention has short time consumption and low energy consumption, can realize low-energy high-speed preparation, and is applied to actual industrial production.

Drawings

FIG. 1 is an XRD diffraction pattern of example, comparative example 1, comparative example 2;

FIG. 2 is SEM pictures of (a) example, (b) comparative example 1, and (c) comparative example 2;

table 1 shows the sheet resistivities of examples, comparative examples 1 and 2.

Detailed Description

In order that the invention may be more readily understood, further details of the invention are provided below with reference to the following examples and the accompanying drawings.

Examples

(1) By using a direct current magnetron sputtering method on Ar and N₂And sputtering the NbTaMoW high-entropy alloy target on a Si single polishing piece in the atmosphere to obtain the coating. The specific technological parameters of the direct current magnetron sputtering are as follows: the target base distance is 8cm, the vacuum degree of a sputtering cavity is lower than 4.3 multiplied by 10^-3Pa, working pressure of 0.3Pa, Ar flow of 38sccm, N₂The flow is 2sccm, the sputtering power is 100W, the sputtering time is controlled to be 8min, and NbTaMoWN is prepared_0.13。

(2) And (2) covering a copper conducting layer on the coating prepared in the step (1) by adopting a direct current magnetron sputtering method. The specific process parameters are as follows: the target base distance is 8cm, the vacuum degree of a sputtering cavity is lower than 4.3 multiplied by 10^-3Pa, the working pressure is 0.3Pa, the Ar flow is 40sccm, the sputtering power is 60W, and the sputtering time is controlled to be 4 min.

(3) And (3) annealing test: and after the magnetron sputtering is finished, annealing at 800 ℃ in a vacuum tube furnace for 60 min.

Comparative example 1

(1) By using a direct current magnetron sputtering method on Ar and N₂And sputtering the NbTaMoW high-entropy alloy target on a Si single polishing piece in the atmosphere to obtain the coating. The specific technological parameters of the direct current magnetron sputtering are as follows: the target base distance is 8cm, the vacuum degree of a sputtering cavity is lower than 4.3 multiplied by 10^-3Pa, working pressure of 0.3Pa, Ar flow of 40sccm, N₂Flow rate of 0sccm, sputteringThe power is 100W, the sputtering time is controlled to be 8min, and NbTaMoWN is prepared.

Comparative example 2

(1) By using a direct current magnetron sputtering method on Ar and N₂And sputtering the NbTaMoW high-entropy alloy target on a Si single polishing piece in the atmosphere to obtain the coating. The specific technological parameters of the direct current magnetron sputtering are as follows: the target base distance is 8cm, the vacuum degree of a sputtering cavity is lower than 4.3 multiplied by 10^-3Pa, working pressure of 0.3Pa, Ar flow of 36sccm, N₂The flow is 4sccm, the sputtering power is 100W, the sputtering time is controlled to be 8min, and the NbTaMoWN is prepared_0.32。

TABLE 1

	Examples	Comparative example 1	Comparative example 2
				Atomic ratio of N	0.13	0	0.32
Square resistivity/mu omega cm	22.38	1.44	45.75

It can be observed from FIG. 1 that for NbTaMoWN_xThe nitride coating, no Cu — Si compound was generated in the examples, comparative example 1 and comparative example 2 at the annealing temperature of 800 ℃, indicating that the diffusion barrier function of the above coating is still effective at 800 ℃. As can be observed from fig. 2, the Cu film surface in comparative example 1 has a large amount of cracks due to the large thermal expansion coefficient of the high-entropy alloy, and the Cu film surface cracks due to expansion at high temperature. The Cu film surface cracking phenomenon in the example and the comparative example 2 was less. As can be seen from Table 1, as the nitrogen content increases, the sheet resistivity increases.

From the above results, it is known that when the N content is too low or even zero, for example, in comparative example 1, when the ratio (x) of N atoms to the sum of Nb, Ta, Mo and W atoms is 0, the electrical properties are good, but the thermal stability of the coating is poor, and defects such as cracking voids occur on the surface at high temperature, and the coating fails; when the N content is too high, for example, in comparative example 2, the ratio (x) of N atoms to the sum of Nb, Ta, Mo and W atoms is 0.32, the thermal stability of the coating is good, but the electrical properties are poor, and the measured sheet resistivity is much larger than that of other examples and comparative example 1, and the coating still fails. From the above results, it is found that as the N content increases, the lattice distortion further increases, the atom packing density increases, and the Cu atom diffusion channel is clogged; and the N atom and other metal atoms can form a covalent bond with large bonding energy, so that the thermal stability and the diffusion shielding performance can be improved by increasing the content of N. However, the increase in the N content reduces the metal bonds in the coating while forming covalent bonds, resulting in an increase in the sheet resistivity of the coating. It is therefore desirable to control the N content, determine the optimum range, and balance the diffusion barrier properties, thermal stability, and electrical properties.

In the selected embodiment of the invention, the ratio (x) of N atoms to the sum of Nb, Ta, Mo and W atoms is 0.13, the content of N is moderate, and the electrical property of the coating is still excellent on the basis of improving the thermal stability of the coating (the square resistivity is 22.38 mu omega cm). And no Cu-Si compound is generated on the surface under the annealing condition of 800 ℃, which shows that the diffusion shielding performance of the coating is still effective, and the comprehensive performance of the coating is obviously superior to that of comparative examples 1 and 2. The thickness of the coating of the embodiment is about 150nm, but most of the coating thicknesses are basically over 500nm at present, and the smaller thickness is also beneficial to further reducing the size of the integrated circuit.

In conclusion, the NbTaMoWN is prepared by the method of direct current magnetron sputtering_xThe nitride coating has simple and rapid process and good repeatability, is in an amorphous phase structure, has small thickness, still has good thermal stability, electrical property and diffusion shielding property under the high temperature condition (the effective working temperature is less than or equal to 800 ℃), and can be applied to an integrated circuit as a diffusion shielding layer in a Cu-Si device.

Claims

1. NbTaMoWN with high-temperature diffusion shielding performance_xThe preparation method of the nitride coating is characterized by comprising the following steps of: by means of DC magnetron sputtering, in N₂5% by weight of Ar and N₂Under the mixed atmosphere, taking NbTaMoW high-entropy alloy as a target material, and sputtering on a Si single polishing piece to obtain NbTaMoWN_xAnd (3) nitride coating.

2. The preparation method according to claim 1, wherein the conditions of the DC magnetron sputtering method are as follows: the target base distance is 7-10 cm, the vacuum degree of the back bottom is lower than 4.3 multiplied by 10^-3Pa, working air pressure of 0.20.4Pa, a total gas flow of 40sccm, an Ar flow of 37-39 sccm, and N₂The flow rate is 1-3 sccm, the sputtering power is 90-110W, and the sputtering time is 6-10 min.

3. NbTaMoWN with high-temperature diffusion shielding performance prepared by the preparation method according to claim 1 or 2_xAnd (3) nitride coating.

4. The NbTaMoWN of claim 3_xThe nitride coating is characterized in that x is 0.1-0.15.

5. The NbTaMoWN of claim 3_xA nitride coating characterized in that x is 0.13.

6. The NbTaMoWN of claim 3_xThe nitride coating is characterized in that the thickness of the coating is 100-200 nm.