TWI395829B - Sputtered copper layer with good properties and method for manufacturing the same - Google Patents

Description

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

The invention relates to a sputtering synthesis method of a copper plating layer, in particular to a sputtering synthesis method for preparing a cerium nitride (RuHfN _x ) added with a trace amount of cerium to dissolve in a copper plating layer, thereby improving the adhesion and conductivity of the copper plating layer. Sex and leakage current properties.

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 property 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 addition of immiscible elements should be the solution, and can be known from the following related literature: such as JP Chu, CH Chung, PY Lee, JM Rigsbee, and JY Wang, "Microstructure and Properties of Cu-C Pseudoalloy Films Prepared by Sputter Deposition", Metallurgical and Materials Transactions A, Vol. 29A, p. 647-658, (1998); JP Chu and TN Lin, "Deposition, Microstructure and Properties of Sputtered Copper Films Containing Insoluble Molybdenum", Journal of Applied Physics, 85, p.6462-6469 (1999); CH Lin, JP Chu, T. Mahalingam, TN Lin and SF Wang, "Thermal Stability of Sputtered Copper Films Containing Dilute Insoluble Tungsten: A Thermal Annealing Study," Journal of Materials Research, Vol. 18, No. 6, p. 1429-1434 (2003); JP Chu and CH Lin, "Formation of A Reacted Layer at The Barrierless Cu (WN)/Si Interface," Applied Physics Letters, Vol. 87, No 21, p. 211902 (2005); SL Zhang, JME Harper and FM D'Heurle, "High conductivity copper-boron alloys obtained by low temperature annealing", Journal of Electronic Materials, Vol. 30, p. L 1, (2001); Zhu Xi, Zhu Xisheng, sputter plating method to make copper coating with antimony to improve the hardness and electrical conductivity of the coating, national invention patent certificate No. 152100 and Zhu Xi, Lin Zongxin, with high temperature stability, good Copper plating layer with conductivity and leakage current properties and its manufacturing method, National Invention Patent Certificate No. 1237328. The immiscible nitride (such as WN _x ) added to the copper film can effectively refine the grain, and the nitrogen of the immiscible nitride precipitates at the grain boundary at a high temperature and reacts with the ruthenium substrate to form a ruthenium compound. (Si ₃ N ₄ ) is effective in reducing the diffusion rate of copper atoms and lowering the electrical resistance.

The use of the Sputter Deposition process to synthesize completely immiscible elements or compounds to form a "supersaturated solid solution" by "Atom-by-atom growth" (Supersaturated Solid Solution) Therefore, it is not limited by the limitations of traditional thermodynamics such as solid solution limit and phase balance, and it is easy to synthesize materials that have been previously considered impossible. The material produced by this method has the characteristics of a metal composite material having a non-equilibrium phase, a nano-scale microstructure, high temperature stability, and high mechanical strength.

The nitrogen energy of the immiscible nitride added to the copper film 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. The sputtering method of copper plating is further reduced by a chemical vapor deposition high-temperature process to greatly reduce process complexity and manufacturing cost.

It is an object of the present invention to provide a sputtering synthesis method for preparing a niobium nitride (RuHfN _x ) to which a trace amount of niobium is added to dissolve in a copper plating layer, thereby improving the adhesion, conductivity and leakage current properties of the copper plating layer.

In order to achieve the above object, the method for sputter plating of the copper plating layer of the present invention comprises: introducing a small amount of nitrogen gas and argon gas in a vacuum sputtering environment, and co-sputtering copper and tantalum or niobium or the like under a mixed state of nitrogen gas and argon gas; An alloy in which the sputtering power of the vacuum sputtering environment is 100-200 watts (W), the sputtering pressure is Ix10 ^-2 to 1 x 10 ^-3 torr, and the copper plating layer is obtained.

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.

Wherein, the sputtering temperature of the vacuum sputtering environment is from normal temperature to I00 °C.

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

Wherein, the copper and the bismuth alloy are co-sputtered to obtain a copper plating layer to be treated, and the synthesis method of the present invention further comprises an annealing treatment process for the copper plating layer to be treated, which is included in the vacuum annealing pressure Ix10 ^- The copper plating layer to be treated was heated at a heating rate of 4 ° C to 6 ° C per minute in an environment of ⁶ to 1 x 10 ^-7 torr, and the annealing temperature was maintained at 200 ° C to 750 ° C for one hour to obtain the copper plating layer.

Wherein, after annealing, the copper plating layer has a resistivity value close to that of the pure copper plating layer, which is about 2 to 3 μΩ-cm.

Wherein, after annealing, the copper plating layer has low leakage current properties, which is about 10 ^-10 ~ 10 ^-9 A/cm ² .

Among them, the copper plating layer has excellent adhesion properties, and its bonding strength is about 10 to 30 MPa.

Among them, the copper plating layer has an excellent TDDB result, which is greater than about 10 years of time-dependent dielectric breakdown voltage (TDDB).

The present invention is also directed to a copper plating layer comprising copper and a group selected from the group consisting of nitrides of tantalum, nitrides of tantalum, and nitrides of tantalum.

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

The material of the invention is a selective element lanthanum nitride (RuHfN _x ), the main purpose of which is to provide a trace metal content and a sputtering process in the copper plating layer, thereby obtaining a superior microstructure, low resistance and low leakage current. nature. Therefore, the copper plating layer containing niobium and its nitride of the present invention has the following originality:

(1) The present invention utilizes a vacuum clean and non-polluting sputtering process, and in the state of introducing a small amount of nitrogen and argon gas, the copper and the ruthenium target are co-sputtered, thereby controlling the ruthenium, ruthenium, or Its alloy and nitride content;

(2) In addition to the high temperature stability and the function of isolating the reaction between copper and bismuth, the copper-plated layer containing cerium nitride precipitated at a high temperature has the following characteristics:

a. Blocking other gases from entering the Passivation layer

b. Blocking the reaction between the copper mats for diffusion barrier

(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 noble metal nitride added by the present invention is different from the previously added immiscible high temperature element, which is also unique to the present invention.

(4) Both copper and niobium nitride (RuHfN _x ) are miscible, and these trace miscible substances are introduced into the copper thin film to prepare a copper plating layer containing a trace amount of miscible substance and formed by annealing the niobium nitride. 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.

In summary, the technology and the alloy composition and properties of the copper plating layer containing the bismuth metal element and the nitride thereof are unprecedented, conform to the requirements of the novel initiative, and are more highly utilized in the industry. Value and applicability.

The method for sputter synthesis of the copper plating layer of the invention comprises introducing a small amount of nitrogen gas and argon gas in a vacuum sputtering environment, and co-sputtering copper and bismuth alloy in a state of mixing nitrogen gas and argon gas to obtain a copper plating layer to be treated. The sputtering power in the vacuum sputtering environment is 150 watts (W), the sputtering pressure is I x10 ^-2 to 1 x 10 ^-3 torr, the sputtering temperature is normal temperature to I00 ° C; the vacuum annealing pressure is Ix10 The copper plating layer to be treated is heated at a heating rate of 4 ° C to 6 ° C per minute in an environment of ^-6 to 1 x 10 ^-7 torr, and the annealing temperature is maintained at 200 ° C to 750 ° C for one hour to obtain the copper plating layer. The content of ruthenium, osmium and nitrogen in the copper plating layer is less than 2.0 atomic percent.

Example

溅, the sputtering synthesis method of the copper plating layer containing cerium nitride of the invention:

In the embodiment of the invention, the copper plating layer containing the bismuth metal element and the nitride is prepared by a DC Magnetron Sputter Deposition process, and the sputtering vacuum system cavity is first pumped to 7 x 10 ^-7. The pressure below torr is then introduced into the vacuum system with high purity argon (Ar) and trace nitrogen (N ₂ ), and the sputtering operation is performed at 150 W energy, and the working pressure of argon/nitrogen is 1*10 ^-2 Torr. Pure copper and bismuth metal elements are used as the material of the sputtering target, and the target is plated by co-sputtering. The ruthenium and nitrogen content required in the copper plating are shown in Table 1. Show), placing the target approximately 20 cm directly below the substrate with the side facing up. The substrate is made of a germanium wafer, and the plating layer is uniform, and the substrate is rotated at a constant speed during the sputtering process. Other important parameters of the sputtering process are shown in Table 2.

Qualitative, quantitative and low resistance of nitrogen and niobium metal elements in tantalum and copper plating:

The bismuth and nitrogen contents 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 the pure Cu, Cu (RuHf) and Cu (RuHfN _x ) coatings before and after annealing according to the ASTM D4541-02 test method. According to the results, the copper coatings containing niobium nitrides are known. It has excellent adhesion properties, and the Cu(RuHfN _x ) coating has good adhesion before and after annealing. The first figure shows the SIMS spectrum of unannealed Cu(Ru(HfNx)). According to this figure, it is known that the plating layer contains Cu, Hf, Ru and N elements. The second figure shows the XPS results for this unannealed coating. According to this figure, both Hf and Ru form a bond with N. The third figure shows the XRD and the selected area of the Cu(RuHfN) before annealing. The two figures show that the Hf ₄ N ₃ phase is formed before annealing, which is consistent with the XPS results. The fourth image shows TEM imaging before and after annealing. The grain size of Cu(HfN) before annealing is 16±3nm, and the grain size of Cu(HfN) after annealing is 110±5nm. There is a native oxide of ~2.7nm at the interface before and after annealing, and there is no copper bismuth compound after annealing. Generated in the interface. According to the diffraction pattern of the selected region after annealing, it is known that there is a trace amount of Hf ₄ N _{3 at the} interface, which needs further confirmation. The fifth figure shows the comparison of the resistivity of Cu(HfN), Cu(RuHfN) and pure copper before and after annealing. According to this figure, the resistance values of Cu (HfN) and Cu (RuHfN) at 630 ° C and 720 ° C were 3.0 and 2.7 μΩ-cm, respectively, and no copper ruthenium compound was formed. The sixth figure shows the leakage current of Cu(RuHfN), Cu(HfN) and pure copper, and the time-dependent dielectric breakdown voltage (TDDB). Based on the results, it can be seen that the addition of a small amount of Ru can reduce the leakage current and reliability of the coating. Better TDDB results.

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. By introducing a nitrogen atom into the plating layer, as described above, the high temperature stability of the copper plating layer can be improved, and low resistance, low leakage current, and good adhesion strength can be obtained.

It can be seen from the above embodiments that the copper plating layer of the present invention has a resistivity value close to the pure copper plating layer and a low leakage current property after passing through different annealing temperatures; and it is excellent before annealing or after different annealing temperatures. Adhesion properties and excellent TDDB results.

The present invention describes the excellent properties of the copper-plated layer containing the bismuth metal element and the nitride by the process of the preferred embodiment and the alloy composition, but it is not intended to limit the present invention, as compared with any study of this study, The technical idea of the invention is to make some changes and changes to achieve the equivalent purpose. Therefore, 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 ruthenium metal element and a nitride having high temperature stability and good electrical conductivity.

The first figure shows a SIMS diagram of the composition of an unannealed Cu(RuHfN) film in an embodiment of the present invention.

The second graph shows the XRD and selective diffraction patterns of an unannealed Cu(RuHfN) film in an embodiment of the present invention.

The third graph shows the leakage current density of Cu (AgNx) annealed at 400 ° C for one hour in the examples of the present invention.

The fourth figure shows Cu (RuHfN) TEM imaging and selective diffraction pattern (c) before (a) annealing and after annealing (b) in the embodiment of the present invention.

The fifth figure shows a comparison of the resistivity of Cu(HfN), Cu(RuHfN) and pure copper in the embodiment of the present invention.

Fig. 6 is a graph showing a comparison of stress time (c) TDDB results of (a) leakage current density (b) fixed electric field strength of Cu(HfN), Cu(RuHfN) and pure copper in the embodiment of the present invention.

Claims (8)

A sputtering method for depositing copper plating includes: introducing a small amount of nitrogen and argon into a vacuum sputtering environment, and co-sputtering copper and tantalum and bismuth or co-sputtering copper and bismuth alloy in a mixed state of nitrogen and argon. The sputtering environment of the vacuum sputtering environment is 100-200 watts (W), the sputtering pressure is 1 x 10 ^-2 ~ 1 x 10 ^-3 torr (torr); and the copper plating layer is obtained; wherein the common sputtering copper and bismuth铪 or co-sputtering copper and bismuth alloy to obtain a copper plating layer to be treated, and the synthesis method of the present invention further comprises subjecting the copper plating layer to be treated to an annealing treatment process, which comprises a vacuum annealing pressure of 1×10 ⁻ The copper plating layer to be treated is heated at a heating rate of 4 ° C to 6 ° C per minute in an environment of ⁶ to 1 x 10 ^-7 torr, and the annealing temperature is maintained at 200 ° C to 750 ° C for one hour to obtain the copper plating layer, and The copper plating layer has a bonding strength of 10 to 30 MPa and a time-dependent dielectric breakdown voltage (TDDB) of more than 10 years. The method for sputter synthesis of a copper plating layer according to claim 1, wherein the copper plating layer has a lanthanum, cerium and nitrogen content of less than 2.0 atomic percent. The method for sputter-synthesizing copper plating according to claim 1, wherein the common sputtered copper and tantalum and the common sputtered copper and tantalum alloy are co-sputtered by a DC magnetron sputtering process. The method for sputter plating of a copper plating layer according to claim 1, wherein the sputtering temperature of the vacuum sputtering environment is from room temperature to 100 °C. A method of sputtering a copper plating layer as described in claim 1, wherein the vacuum sputtering environment has a sputtering power of 150 watts (W). The method for sputter plating of a copper plating layer according to any one of claims 1 to 5, wherein the copper plating layer has a thickness of 2 to 3 μΩ-cm when the annealing temperature ranges from 630 to 720 °C. The resistivity value, after annealing, the copper plating layer has a leakage current property of 10 ^-10 to 10 ^-9 A/cm ² . A copper plating layer produced by the sputtering synthesis method of the copper plating layer according to any one of claims 1 to 6, which comprises copper and tantalum nitride, and the copper plating layer has a thickness of 10 to 30 MPa. Intensity and time dependent dielectric breakdown voltage (TDDB) greater than 10 years. The copper plating layer of claim 7, wherein the cerium, lanthanum and nitrogen contents are each less than 2.0 atomic percent.