TWI408244B - New technique for fabrication of copper films with excellent properties - Google Patents

Abstract

In this study, a co-sputter deposition technique for the fabrication of novel copper films containing a small amount of Re, Ta and N elements (ReTaNx) is proposed, and the composition and properties of these films are investigated. This technique can be used for the deposition of copper alloy films on copper electrodes. This technique is simple and can be used to obtain copper films containing up to 2 atomic percent of Re, Ta, and N elements. The proposed technique involves co-sputtering of ReTaNx and copper targets in pure Ar atmosphere or Ar/N2 atmosphere for fabricating Cu(ReTaNx) films. By controlling the amounts of Re, Ta and N, copper films containing the desired amounts of elements [Cu(ReTaNx)] can be obtained. These films have excellent properties such as good adhesion properties, high electrical resistance, and low leakage current. These films are found to be superior to pure copper films in term of their properties.

Description

Copper plating layer with good alloy film properties and manufacturing method thereof

The invention relates to a copper plating layer, in particular to a copper plating layer containing a trace amount of niobium nitride (ReTaN _x ) by magnetron sputtering, thereby improving the adhesion and conductivity of the copper plating layer and reducing the leakage current density thereof.

Copper and its alloys are widely used because of their excellent electrical conductivity, heat transfer and good room temperature mechanical properties. However, copper and copper alloys have poor mechanical properties at high temperatures, so the effective use of these alloy materials The temperature is not so high that its good electrical conductivity and heat transfer properties cannot be effectively used, which makes the material subject to many restrictions. In recent years, in addition to excellent electrical conductivity, copper has a high charge-migrating resistance, which makes the components of the copper wire have higher life and stability, and thus replaces aluminum as a conductive layer in a semiconductor element. The copper-plated film has added more effective use value in application; however, there are still some limitations in the use of the copper conductive layer in terms of process or material, such as poor adhesion and easy reaction with ruthenium. However, after the addition of the alloying elements, the conductivity of the copper decreases and the hardness value increases. Therefore, the solution should be solved by adding immiscible elements, and can be known from the following related documents: such as JP Chu, CH Chung, PY Lee, JM Rigsbee, and JY Wang, Metallurgical and Materials Transactions A , Vol. 29A, p. 647-658, (1998); JP Chu and TN Lin, Journal of Applied Physics , 85, p.6462-6469, (1999); CH Lin, JP Chu, T. Mahalingam, TN Lin and SF Wang, Journal of Materials Research , Vol. 18, No. 6, p. 1429-1434 (2003); JP Chu and CH Lin, Applied Physics Letters , Vol. 87, No. 21, p. 211902 (2005); SL Zhang, JME Harper and FM D'Heurle, Journal of Electronic Materials , Vol. 30, p. 11-30, (2001); Zhu Xi, Zhu Xisheng, "Spray-plated copper coatings containing tantalum to enhance the hardness and electrical conductivity of the coating" , TW invention patent certificate No. 152100; Zhu Xi, Lin Zongxin, "Copper plating with high temperature stability, good electrical conductivity and leakage current properties and its manufacturing method", TW invention patent certificate No. I237328.

It can be known from the above related literatures and patents that the immiscible nitride (such as WN _x ) added to the copper film can effectively refine the grain, and the nitrogen of the immiscible nitride will crystallize at high temperature. The boundary precipitates and reacts with the ruthenium substrate to form a nitrogen ruthenium compound (Si ₃ N ₄ ) to effectively reduce the diffusion rate of copper atoms and reduce the electrical resistance, and such techniques generally require a chemical vapor deposition (CVD) process. In order to prevent the diffusion of copper atoms by forming immiscible nitride on the copper film; however, in the trend of smaller components, higher density, and increasingly thinner barrier layers, The problems of increasing the overall resistance of the derivative and the inability to develop a barrier layer that is both thin (<2 nm) and resistant to high temperatures need to be addressed. Therefore, how to effectively reduce the manufacturing cost, and also to develop a profitable and forward-looking copper plating preparation method in response to the demand for the advanced copper metallization process of the future unobstructed layer, will be an urgent problem to be solved.

The nitrogen energy of the immiscible nitride added to the copper plating layer reacts with the ruthenium substrate at a high temperature to form a nitrogen ruthenium compound as a barrier layer; and the inventors have innovatively developed a barrier layer capable of spontaneous generation without the need for a barrier layer. A method of manufacturing a copper plating layer by a high-temperature process by chemical vapor deposition to greatly reduce process complexity and manufacturing cost. In view of the fact that there is no copper coating on the properties of good adhesion, electrical conductivity and leakage current, the copper plating has finally been invented through continuous research and experimentation.

The object of the present invention is to prepare a trace amount of niobium nitride (ReTaN _x ) by a magnetron sputtering method to dissolve in a copper plating layer, thereby improving the adhesion and conductivity of the copper plating layer and reducing the leakage current density thereof.

In order to achieve the above object, a method for manufacturing a copper plating layer having good alloy film properties of the present invention comprises: introducing a small amount of nitrogen gas and argon gas in a vacuum sputtering environment, and co-sputtering copper with a mixed state of nitrogen gas and argon gas;铼, 钽 or an alloy thereof, wherein the sputtering power of the vacuum sputtering environment is 100 to 200 watts (W), the sputtering pressure is 1 × 10 ^-2 to 1 × 10 ^-3 torr (torr); and a copper is obtained Plating.

Wherein, the content of lanthanum, cerium and nitrogen in the copper plating layer is less than 2.0 atomic percent.

Among them, the above copper and bismuth alloys are co-sputtered by a DC magnetron sputtering process.

The sputtering temperature of the vacuum sputtering environment is from room temperature to 100 ° C.

Among them, the vacuum sputtering environment has a sputtering power of 150 watts (W).

Wherein, after the common sputtering of the copper and the bismuth alloy, a copper plating layer to be treated is obtained, and the copper plating layer to be processed is further subjected to an annealing treatment process, which is performed at a vacuum annealing pressure of 1×10 ^-6 to 1×. The copper plating layer to be treated is heated at a heating rate of 4 ° C to 6 ° C per minute in a 10 ^-7 torr environment, and the annealing temperature is maintained at 200 ° C to 750 ° C for one hour to obtain the copper plating layer. .

Wherein, after annealing, the leakage current density of the copper plating layer is reduced, which is about 1×10 ^-11 to 5×10 ⁻¹⁰ A/cm ² .

Among them, the copper plating layer has excellent adhesion properties, and its bonding strength is about 5 to 25 Mpa.

Among them, the copper plating layer has excellent time dependence dielectric breakdown (TDDB) results, which is at a field electric field strength of 0.9 MV/cm and does not cause dielectric breakdown before Cu(ReTaN _x ) plating Has a life span of more than 10 years.

The present invention is also directed to a copper plating layer having good alloy film properties including copper and a group selected from the group consisting of nitrides of tantalum, nitrides of niobium, and niobium nitrides.

Among them, the lanthanum, cerium and nitrogen contents are each less than 2.0 atomic percent.

The use of magnetron sputtering to synthesize completely immiscible elements or compounds to form a "supersaturated solid solution" in the form of atom-by-atom growth. Limited by traditional thermodynamics such as solid solution limits and phase equilibrium, it is easy to synthesize materials that were previously considered impossible. The materials produced by this method have the characteristics of a metal composite material having a non-equilibrium, nano-scale microstructure, high temperature stability, and high mechanical strength. The material added to the copper plating layer of the present invention is selected from tantalum nitride (ReTaN _x ), and its main purpose is to provide a trace metal content and a sputtering process in the copper plating layer, thereby obtaining good adhesion, low resistance and low leakage. The superior nature of current. Therefore, the copper plating layer of the present invention having good alloy film properties has the following originality:

(1) The present invention utilizes a vacuum clean and non-polluting sputtering process, and in the mixed state of introducing a small amount of nitrogen and argon, the copper and the bismuth target are co-sputtered, thereby controlling the ruthenium in the copper plating layer. Nitride content:

(2) The self-passivation layer formed by depositing the copper plating layer at a high temperature in the present invention has high temperature stability and a function of isolating the reaction between copper and bismuth, and has the following characteristics:

a. can act as a passivation layer to block the entry of other gases;

b. It can act as a diffusion barrier that blocks the interaction of copper and bismuth.

(3) Since the present invention can naturally form a barrier layer which is a spontaneously formed product, it is not necessary to obtain a barrier layer by a chemical vapor deposition high temperature process; therefore, copper can be obtained by the method of the present invention. The combination of the plating layer and the barrier layer is one, which greatly reduces the process complexity and manufacturing cost. It can be seen that the characteristics which the niobium nitride added in the copper layer of the present invention can produce are different from the addition of the previously immiscible high temperature element, which is also unique to the present invention.

(4) Both copper and bismuth nitride (ReTaN _x ) are slightly miscible, and the copper plating layer obtained by introducing these trace miscible substances into the copper thin film is annealed and then formed by the precipitation of niobium nitride. The layer has high temperature stability, good adhesion, low resistivity value and leakage current property. It is a good conductive coating suitable for semiconductor, optoelectronic and other related industries, and can improve the current copper process technology.

The invention relates to a method for manufacturing a copper plating layer having good alloy film properties, which comprises introducing a trace amount of nitrogen gas and argon gas in a vacuum sputtering environment, and co-sputtering copper and bismuth alloy together in a state of mixing nitrogen gas and argon gas to obtain a waiting condition. Treated copper plating, in which the sputtering power of the vacuum sputtering environment is 150 watts (W), the sputtering pressure is 1 × 10 ^-2 to 1 × 10 ^-3 torr, and the sputtering temperature is from room temperature to 100 ° C. The copper plating layer to be treated is heated at a temperature of 4 ° C to 6 ° C per minute in an environment having a vacuum annealing pressure of 1 × 10 ^-6 to 1 × 10 ^-7 torr, and the annealing temperature is in the range of 200 The temperature was maintained at ° C to 750 ° C for one hour to obtain the copper plating layer, and the content of lanthanum, cerium and nitrogen in the copper plating layer was less than 2.0 atomic percent.

Example

壹, the method for manufacturing the copper plating layer with good alloy film properties of the invention and various process parameters:

The copper plating layer with good alloy film properties of the present invention is obtained by the DC magnetron Sputter Deposition process in the embodiment of the present invention, and the sputtering vacuum system cavity is first controlled at 7×10 ^{-7 .} Under the pressure of the torr, the high-purity argon (Ar) and the trace amount of nitrogen (N ₂ ) are introduced into the vacuum system to adjust the sputtering working pressure to 1×10 ^-2 torr, and 150W of energy for sputtering work. Pure copper and bismuth metal elements are used as the material of the sputtering target, and the target is plated by co-sputtering; the target is placed approximately 20 cm directly below the substrate, and Face up. The substrate is a tantalum wafer. In order to achieve uniform plating, the substrate during the sputtering process is rotated at a constant speed. The important parameters of other sputtering processes are shown in Table 2.

定 Qualitative, quantitative and electrical resistance determination of elemental contents of nitrogen and niobium nitride in copper plating:

The contents of ruthenium, osmium and nitrogen in the copper plating layer of the present invention were respectively measured by an electronic microprobe analyzer (EPMA), and the composition thereof is shown in Table 1. Table 3 shows the comparison of the adhesion strength measurements of pure Cu, Cu (ReTa) and Cu (ReTaN _x ) coatings before and after annealing according to ASTM D4541-02. Based on this result, it is known that Cu (ReTaN _x ) niobium nitrogen is contained. The copper coating of the compound has excellent adhesion properties, and the Cu (ReTaN _x ) coating has good adhesion before and after annealing.

The Cu (ReTa), Cu (ReTaN _x ) and pure copper plating layers shown in Fig. 1 are the resistance measurement results after annealing at different temperatures. According to the figure, it can be seen that the Cu (ReTaN _x ) coating after annealing at 750 ° C can reach a low resistance value of 2.35 μΩ-cm.

Figure 2 shows the comparison of leakage current results for Cu (ReTa), Cu (ReTaN _x ) and pure copper plating. According to the results, the current density per unit area of the Cu (ReTaN _x ) plating layer after annealing at 400 ° C is the lowest of the three, and the system is about 10 ^-11 to 10 ^-10 A / cm ² , and the result is If the copper plating layer containing the bismuth alloy is further added, if a small amount of nitrogen is added, the leakage current density of the copper plating layer can be lowered.

Figure 3 shows the comparison of time dependence dielectric breakdown (TDDB) results for Cu(ReTa), Cu(ReTaN _x ) and pure copper coatings. According to the results, it can be seen that if the three coatings have the same electric field strength, the Cu (ReTaN _x ) coating containing a trace amount of nitrogen can obtain a reliable time-dependent dielectric breakdown (TDDB) result, and is 0.9 MY/cm. The Cu(ReTaN _x ) coating has a lifetime of more than 10 years before the electric field strength and without causing dielectric breakdown.

Figure 4 shows the results of resistance measurements of Si/SiO ₂ /TaN/Cu(ReTaN _x ) after annealing at different temperatures. From this result, it can be seen that Si/SiO ₂ /TaN/Cu(ReTaN _x ) after annealing at 660 ° C can reach a low resistance value of 3.24 μΩ-cm.

Figure 5 shows the reliability of Si/SiO ₂ /TaN/Cu(ReTaN _x )/Ta ₂ O ₅ /Pt metal insulator metal (MIM) capacitors with Cu(ReTaN _x ) as the lower electrode at the same electric field strength. The preferred TDDB characteristics, and the Cu (ReTaN _x ) coating has a lifetime of more than 10 years before the electric field strength of 1.72 MV/cm and without causing dielectric breakdown.

Properties of copper coatings of ginseng, niobium containing elements and their nitrides:

In the examples of the present invention, the copper plating properties of the cerium-containing element and its nitride are mainly described. The introduction of nitrogen atoms in the copper plating layer can improve the high temperature stability of the copper plating layer, and obtain low resistance, low leakage current density and good adhesion.

According to the above embodiments, the copper plating layer of the present invention has a resistivity and a low leakage current property close to the pure copper plating layer after different annealing temperatures; and is excellent before and after annealing or after different annealing temperatures. Adhesion properties and excellent TDDB characteristics.

The present invention describes the excellent properties of the copper-plated layer containing metal niobium nitride by the process and alloy composition of the preferred embodiment. However, it is not intended to limit the present invention, and thus it is common in the art to have a waiter in the art. Under the principles and concepts of the present invention, some changes and modifications are made in accordance with the technical idea of the present invention, but they are all within the scope of the present invention. The scope of protection of the present invention should include the principles of the sputtering technique of the present invention to achieve a copper plating layer containing a metal element niobium nitride having high temperature stability and good electrical conductivity.

1 is a graph showing the results of resistance measurement of Cu (ReTaN _x ) before and after annealing in an embodiment of the present invention.

2 is a comparison diagram of leakage current results of Cu (ReTa), Cu (ReTaN _x ) and pure copper in an embodiment of the present invention.

3 is a comparison diagram of TDDB results of Cu (ReTa), Cu (ReTaN _x ) and pure copper in an embodiment of the present invention.

4 is a graph showing the results of resistance measurement of Si/SiO ₂ /TaN/Cu (ReTaN _x ) before and after annealing in the embodiment of the present invention.

5 is a graph showing measurement results of a Si/SiO ₂ /TaN/Cu(ReTaN _x )/Ta ₂ O ₅ /Pt MIM capacitor using Cu(ReTaN _x ) as a lower electrode in an embodiment of the present invention.

Claims (14)

A method for manufacturing a copper plating layer having good alloy film properties: introducing a small amount of nitrogen gas and argon gas in a vacuum sputtering environment, and co-sputtering copper and bismuth alloy in a mixed state of nitrogen gas and argon gas to obtain a copper to be treated a plating layer in which a sputtering power of a vacuum sputtering environment is 100 to 200 watts, a sputtering pressure is 1 × 10 ^-2 to 1 × 10 ^-3 Torr, and an annealing process for the copper plating layer to be processed is performed In the environment of vacuum annealing pressure of 1×10 ^-6 to 1×10 ^-7 Torr, the copper plating layer to be treated is heated at a temperature of 4° C. to 6° C. per minute, and the annealing temperature ranges from 200° C. to The temperature was maintained at 750 ° C for one hour to obtain an annealed copper plating layer; wherein the annealed copper plating layer had a low leakage current density of about 1 × 10 ^-11 to 5 × 10 ^-10 A/cm ² . A method for producing a copper plating layer having good alloy film properties as described in claim 1, wherein the copper plating layer has a lanthanum, cerium and nitrogen content of less than 2.0 atomic percent. A method for manufacturing a copper plating layer having good alloy film properties as described in claim 1, wherein the copper and tantalum alloys are co-sputtered by a DC magnetron sputtering process. The method for producing a copper plating layer having good alloy film properties as described in claim 1, wherein the vacuum sputtering environment has a sputtering temperature of from room temperature to 100 °C. A method of manufacturing a copper plating layer having good alloy film properties as described in claim 1, wherein the vacuum sputtering environment has a sputtering power of 150 watts. The method for producing a copper plating layer having good alloy film properties as described in claim 1, wherein the annealed copper plating layer has excellent adhesion properties and a bonding strength of about 5 to 25 MPa. A method for producing a copper plating layer having good alloy film properties as described in claim 1, wherein the annealed copper plating layer has a larger than an electric field strength of 0.9 MV/cm and does not cause a dielectric breakdown. 10 years of life. A copper plating layer having good alloy film properties, comprising copper and a group selected from the group consisting of niobium nitride, tantalum nitride, and niobium alloy nitride, and the copper plating layer has about 1×10 ⁻ Low leakage current density of ¹¹ to 5 × 10 ^-10 A/cm ² . A copper plating layer having good alloy film properties as described in claim 8 wherein the ruthenium, osmium and nitrogen contents are each less than 2.0 atomic percent. A copper plating layer having good alloy film properties as described in claim 8 wherein the copper plating layer has excellent adhesion properties and has a bonding strength of about 5 to 25 MPa. A copper plating layer having good alloy film properties as described in claim 8 wherein the copper plating layer has a lifetime of more than 10 years before an electric field strength of 0.9 MV/cm and without causing dielectric breakdown. A copper plating layer having good alloy film properties, which is produced by the manufacturing method according to claim 1, wherein the copper plating layer has about 1×10 ^-11 to 5×10 ^-10 A/cm. ² low leakage current density. A copper plating layer having good alloy film properties as described in claim 12, wherein the copper plating layer has excellent adhesion properties, and the subsequent strength is about 5 to 25 MPa. A copper plating layer having good alloy film properties as described in claim 12, wherein the copper plating layer has a lifetime of more than 10 years before an electric field strength of 0.9 MV/cm and without causing dielectric breakdown.