TW201910559A - Copper-silver two-component metal plating liquid for semiconductor wires and plating method comprising copper methanesulfonate, silver methanesulfonate, methanesulfonic acid, chloride ions and water - Google Patents

Abstract

A copper-silver two-component metal plating liquid which comprises: copper methanesulfonate, silver methanesulfonate, methanesulfonic acid, chloride ions and water. The present invention further provides a plating method for forming a copper-silver two-component metal by using the electroplating liquid, the steps comprising: (a) contacting the copper-silver two-component metal plating liquid with a substrate; (b) applying a working voltage, controlling the current density of the voltage between 0.1 and 2 ASD and electroplating the substrate. As a result, through the design of the electroplating liquid of methanesulfonic acid and methanesulfonate, the plating liquid has environmentally-friendly characteristics such as low poisoning hazards. In addition, during electroplating, with the adjustment of potential and current, a copper-silver two-component metal plating layer with a specific silver content can be obtained.

Description

 Copper-silver two-component metal plating liquid for semiconductor wires and plating method  

The present invention relates to a two-component metal plating liquid and a plating method, and more particularly to a copper-silver two-component metal plating liquid and a plating method. The invention can be applied to the fabrication of wires for semiconductor circuits, and the copper-silver two-component metal plating layer helps to suppress electromigration.

As the related electronic products such as computers, communication and handheld devices continue to pursue the improvement of component performance, and in response to the trend of miniaturization, high speed and high capacity of microelectronic products, the interconnection of transistor components and wafer carriers The design of the interconnect is continuously limited. When the wire size is less than 500 nm, the current density will be as high as 106 Amp/cm ² .

In response to the trend of miniaturization, high speed and high capacity of microelectronic products, the interconnect design of the transistor component and the wafer carrier is continuously limited, and the current density of the wire is rapidly increased (>105Amp/ Cm ² ). However, a high-density current may be generated by a wire or a hillock between the wires, such that the wire has an electromigration effect to cause a short circuit or an open circuit. Therefore, the reliability of the wire becomes an important issue. Copper alloy wires are considered to be potential solutions to the electromigration of electronic wires. According to the 2007 ITRS (international technology roadmap for semiconductor) specification of the wire selection, the specific resistance value is an important index, and its value must be less than 2.2μΩ cm. Compared with the specific resistance value of the copper-plated wire, it is 1.7~1.9μΩ cm. The difference between the specific resistance and the resistance value should be considered in selecting the copper alloy wire. Because silver has excellent electrical conductivity, the copper-silver alloy wire is considered to be possible appropriate improvement. Program. According to different silver content and deposition mode, the copper-silver alloy film has a specific resistance value of about 2.0~3.0μΩ cm. Compared with copper metal, the mechanical strength and electromigration resistance are improved.

Research on copper-silver metal plating systems and their copper-silver coatings, such as S. Strehle et al., an acidic formulation plating system using copper sulphate silver (Thin Solid Film, 519, 3522 (2011), Thin Solid Films, 517.11, 3320). (2009), Microelectronic Engineering, 87.2, 180 (2010)), for the first time on copper-silver metal plating as a discussion of electromigration of electronic wires, which consists of a plating solution of an aqueous solution of copper sulfate, silver nitrate and sulfuric acid, and adjusts the silver nitrate The added concentration (1.5x10 ^-4 ~3x10 ^-3 M) and current density (0.5~3ASD) are used as the control of the silver content of the coating. The thickness of the copper-silver coating is 1μm, and the silver content in the coating can be controlled at 0~4at. %. MJKim et al. used copper cyanide plating solution for alkaline copper cyanide plating (J. Electrochem. Soc., 159, D253 (2012)), which mainly carried out LSV analysis and copper-silver metal plating process development. In addition, Bernasconi et al. published a copper pyrophosphate/silver plating solution (ECS Transactions, 58.32, 53 (2014)), mainly using the process current density of 2~5 mA/cm2 as the control silver content, and the results showed that the silver content of the coating was 3~16at.%; as the current density increases, the silver content of the coating decreases. U.S. Patent No. 7,821,135 uses an alkaline plating system of pyrophosphoric acid or ethylenediamine. However, the above studies did not mention how the acidic solution can avoid the precipitation of AgCl during the electroplating process and lead to the effect of electroplating; in addition, it is difficult to consider the toxic characteristics of the plating solution such as copper sulfate and cyanide and the use of photoresist in the wire definition process. Industrial application.

Therefore, the industry needs an innovative copper-silver two-component metal plating liquid and electroplating method. The plating solution has environmentally friendly characteristics such as low poisoning hazard, and avoids possible precipitation phenomenon in the electroplating process to prepare copper and silver according to industry requirements. Two-component metal material.

In view of the above-mentioned shortcomings of the prior art, the main object of the present invention is to provide a copper-silver two-component metal plating liquid and a plating method, wherein the methanesulfonic acid and the methanesulfonate are biodegradable and selective in the selection of the plating solution. Environmentally friendly characteristics such as lower poisoning hazard; in terms of process, copper methane sulfonate is a copper ion plating solution with high concentration, which can provide process characteristics of high current density deposition. In addition, this system can follow the additives of the traditional acidic copper sulfate plating solution system.

In order to achieve the above object, according to the solution proposed by the present invention, a copper-silver two-component metal plating liquid and a plating method comprising copper methanesulfonate, silver methanesulfonate, methanesulfonic acid, chloride ion and water are provided. In combination with the precise potential and current control of the electroplating process, a copper-silver two-component metal coating with a specific silver content can be obtained.

The invention uses a plating liquid system mainly composed of methanesulfonic acid and methanesulfonate. In order to avoid precipitation of silver chloride in the plating solution, a sulfur-containing double bond thiourea compound can be further introduced and added to the plating liquid system. , forming a silver ion with silver ions. The thiourea compound is (R ₁ R ₂ N)(R ₃ R ₄ N)C=S, wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen or a hydrocarbon group of the same or different species, wherein the hydrocarbon group The carbon number may be from 1 to 6; the thiourea compound may be thiourea, diethyl thiourea, phenylthiourea, allyl thiourea, diphenyl thiourea or one of the group consisting of.

In the above, the molar concentration of the copper methanesulfonate is between 0.05 and 0.8 M; the molar concentration of the silver methanesulfonate is between 0.1 and 6 mM; the volume of the chloride ion The ear concentration is between 0.1 and 3 mM; the thiourea compound has a molar concentration of 5 to 10 times that of the silver methane sulfonate.

The copper-silver two-component metal plating liquid in the above may further comprise a surfactant, the surfactant may be a polymer compound, and the molecular weight is between 2,000 and 20,000; the surfactant may be polyethylene glycol, poly Propylene glycol or a group of propylene glycol; the addition of surfactants can enhance the adsorption in the high current end region, and interact with chloride ions to increase the polarization effect, thereby inhibiting the deposition of copper ions at the high current end, thereby improving the flatness of the coating.

The above-mentioned surfactants may also be the surfactant products used in the current semiconductor circuit process, and usually contain an accelerator and a suppressor.

The invention adopts a copper/silver methanesulfonate plating solution for metal plating, which is different from the conventional acidic copper sulfate/silver nitrate or alkaline cyanide system, and can avoid silver chloride in the plating solution. The state of deposition and cyanide use is expected to be applied to semiconductor wire processes.

The invention further provides a copper-silver two-component metal plating method, the steps comprising: (a) providing the copper-silver two-component metal plating liquid in the above contact with a substrate; (b) applying an operating voltage to control the current of the voltage The substrate was electroplated at a density between 0.1 and 2 ASD (current density, A/dm ² ).

In the above, the substrate may be a plate, a wire, a concave portion or a convex portion; the material of the substrate may be a metal substrate, a glass substrate, a ceramic substrate or a polymer substrate.

The invention further provides a copper-silver two-component metal plating layer prepared by the copper-silver two-component metal plating method as described above, wherein the copper-silver two-component metal plating layer has a silver content of between 0.1 and 40% by weight.

The invention relates to a copper-silver two-component metal plating liquid and an electroplating method, which is characterized in that an acidic copper sulfonate plating liquid system can be used to allow a chloride ion concentration of 0 to 100 ppm, and a photoresist is used in a semiconductor circuit definition process. The electroplating liquid system of the present invention has a better tolerance than the alkaline plating system. In addition, the plating solution of the present invention has environmentally-friendly characteristics such as lower poisoning hazard, and the introduction of a sulfur-containing double bond thiourea compound can avoid the precipitation phenomenon which may exist in the electroplating process. In the electroplating method, the film is fabricated in a precision controlled voltage/current plating system, and the copper-silver two-component metal plating layer having a specific silver content can be controlled, and the obtained copper-silver two-component metal plating layer can have a silver content of 0.1 or less. Between 40% by weight. The invention can be applied to the fabrication of wires for semiconductor circuits, and the copper-silver two-component metal plating layer helps to suppress electromigration.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the manner, the Other objects and advantages of the present invention will be described in the following description and drawings.

100‧‧‧Electroplating system installation

110‧‧‧Power supply

120‧‧‧Reactor

121‧‧‧Electrochemical solution

122‧‧‧ cathode

123‧‧‧Anode

124‧‧‧Spray device

201‧‧‧Insulation

202‧‧‧Barrier layer

203‧‧‧Copper wire/copper and silver two-component metal wire

204‧‧‧Insulation

205‧‧‧Wire microstructure

206‧‧‧resist layer or barrier layer

207‧‧‧ seed layer

208‧‧‧copper film/copper-silver two-component metal film

209‧‧‧Copper wire/copper and silver two-component metal wire

The first figure is a schematic diagram of copper-silver two-component metal plating according to the present invention; the second figure is a relationship between the silver content and the potential of the copper-silver two-component metal plating layer of the embodiment of the present invention; the third figure is the copper of the embodiment of the present invention. A scanning electron microscope image of a silver two-component metal plating layer; the fourth drawing is a schematic diagram of a copper-silver two-component metal microelectronic wire structure of the present invention; and the fifth figure is a copper-silver two-component metal microstructure wire of the present invention. Process description chart (flows (A) to (C)); the sixth figure is a process description diagram of the copper-silver two-component metal microstructure wire of the present invention (flows (D) to (E)).

The embodiments of the present invention are described by way of specific examples, and those skilled in the art can readily appreciate the advantages and effects of the present invention from the disclosure herein.

The invention provides a copper-silver two-component metal plating liquid and a plating method, which can be applied to the production of copper-silver two-component metal wires. The methanesulfonic acid chemical electroplating system proposed by the invention adopts methanesulfonic acid and methanesulfonate as main components, including copper methanesulfonate, silver methanesulfonate, methanesulfonic acid, chloride ion and Water, and can introduce sulfur-containing double bond thiourea compounds, added to the plating system to form silver ions with silver ions to avoid possible precipitation phenomenon in the plating process. The present invention may further comprise a surfactant, which may be a polymer compound having a molecular weight of between 2,000 and 20,000; the surfactant may be polyethylene glycol, polypropylene glycol or a group consisting of the same.

The invention further provides a copper-silver two-component metal plating method, the steps comprising: (a) providing the copper-silver two-component metal plating liquid in the above contact with a substrate; (b) applying an operating voltage to control the current of the voltage The substrate was electroplated at a density between 0.1 and 2 ASD (current density, A/dm ² ).

The invention further provides a copper-silver two-component metal plating layer prepared by the copper-silver two-component metal plating method as described above, wherein the copper-silver two-component metal plating layer has a silver content of between 0.1 and 40% by weight.

Please refer to the first figure, which is a schematic diagram of copper-silver two-component metal plating according to the present invention. As shown, the present invention employs a precision power supply unit and a reactor for electroplating. The power supply 110 has a precise function of constant potential, constant current and electric energy calculation, and the reactor 120 has a good bath circulation function and a sandwich design of fixed electrodes. The electroplating chemical solution 121 mainly comprises a methylsulfonic acid and a methanesulfonate, and a thiourea compound is introduced to form a silver ion with a silver ion. By regulating the concentration of chemicals such as copper ions, silver ions, sulfur double bond polymers and chloride ions in electroplating chemicals, and matching the precise potential/current control, a copper-silver two-component metal coating with a specific silver content can be obtained.

 Example: copper-silver two-component metal plating  

In this embodiment, the configuration of the copper-silver two-component metal plating solution proposed by the present invention is employed as an evaluation of the plating method and the plating characteristics. The configuration contents of the plating solution are copper methanesulfonate 0.63M, silver methanesulfonate 0.001M, methanesulfonic acid 1.04M, thiourea 0.01M, chloride ion 40 ppm, surfactant (polyethylene glycol) 20 ml/L. As shown in Table 1, the configuration capacity is 1 liter. The substrate is made of 2x2cm ² twinned substrate, the surface of which has 100nm barrier layer of tantalum nitride material and 200nm copper seed layer, and the substrate is placed at the cathode of the electroplating system. The anode is a platinum electrode. The electroplating process is controlled by constant current, the current density is controlled at 1 amp/dm ² , and the stirring solution (300 rpm) is used to assist the plating solution cycle. By observing the electric quantity accumulated in the electroplating process to 11 coulomb, the electroplating procedure is completed, and the plating of this embodiment is performed. The thickness is 1 μm.

Please refer to the second figure, which is a diagram showing the relationship between the silver content and the potential of the copper-silver two-component metal plating layer according to an embodiment of the present invention. As shown in the figure, with the adjustment of the plating potential, the prepared copper-silver two-component metal plating layer can control the silver content between 0 and 40 wt%, indicating that the present invention cooperates with a precise power supply as a constant potential/constant current. Controlled to obtain a copper-silver two-component metal coating of a specific silver content.

Please refer to the third figure, which is a scanning electron microscope image of a copper-silver two-component metal plating layer according to an embodiment of the present invention. As shown in the figure, the cross section of the copper-silver two-component metal plating layer (silver content: 3.25 wt%) of the example was observed through an electron microscope, the crystal lattice was columnar, and had a twin-iamella microstructure, showing The invention can be applied to the fabrication of wires for semiconductor circuits, and the copper-silver two-component metal plating layer helps to suppress electromigration.

Please refer to the fourth figure for a schematic diagram of the structure of the copper-silver two-component metal microelectronic wire of the present invention. The wire process is as shown in the fifth and sixth figures. Figure 5 (A) shows the micro-wire structure (groove or hole). The method is implemented on the insulating substrate 201 (矽 or ceramic), which contains the barrier layer. 202 (barrier layer) and copper wire or copper / silver bimetallic component wire 203. After the fabrication of the insulating layer 204 is completed over 201, the wire microstructure 205 is completed by line pattern definition and etching. Figure 5 (B) shows the fabrication of a barrier layer in the wire microstructure, which is usually a high melting point material such as titanium, titanium nitride, tungsten nitride, and nitride. Tungsten, tantalum, tantalum nitride; the method may be PVD (physical vapor deposition) or CVD (chemical vapor deposition). FIG. 5(C) shows the growth of the seed layer 207. Usually, the film of the copper material is completed by PVD to serve as a subsequent plating film process. Figure 5 (D) shows the application of an electroplating process to complete a copper film/copper-silver two-component metal film 208 on the surface of the insulating layer 204 and the microstructure 205 by adjusting an appropriate copper sulfonate silver plating solution and adjustment of the plating process parameters. . Fig. 5(E) shows the fabrication of the microstructured wire 209 by electroplating a thin film layer by precision mechanical polishing (CMP).

As shown in Figure 5(D), the electroplated film layer can be applied to the microstructured wire process. The copper/silver wire is fabricated on the microstructured surface 205 of the insulating layer 201 or the insulating layer 204 by adjusting the appropriate copper sulfonate silver plating solution and the adjustment of the plating process parameters, and the electromigration resistance is excellent. As an improvement in wire quality reliability.

The copper-silver two-component metal plating liquid and the electroplating method of the invention pass through the design of the electroplating liquid of the methanesulfonic acid and the methanesulfonate, so that the plating solution has the environmentally-friendly characteristics of lower poisoning hazard; and by the thiourea The compound is introduced into the plating liquid to avoid possible precipitation phenomena in the electroplating process. With the adjustment of the potential (current) during electroplating, the prepared copper-silver two-component metal plating layer can control the silver content between 0.1 and 40 wt%, indicating that the present invention is matched with a precise power supply as a constant potential/constant current. Controlled to obtain a copper-silver two-component metal plating layer having a specific silver content, and the crystal lattice thereof is columnar and has a twin-lamella microstructure, which shows that the present invention can be applied to the fabrication of wires for semiconductor circuits. In order to suppress the phenomenon of electromigration, it will be more widely used in the future.

The above-described embodiments are merely illustrative of the features and effects of the present invention and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

Claims (12)

 A copper-silver two-component metal plating liquid comprising: copper methanesulfonate, silver methanesulfonate, methanesulfonic acid, chloride ion and water.    The copper-silver two-component metal plating liquid according to claim 1, wherein the copper methanesulfonate has a molar concentration of 0.05 to 0.8 M.    The copper-silver two-component metal plating liquid according to claim 1, wherein the silver methanesulfonate has a volume molar concentration of between 0.1 and 6 mM.    The copper-silver two-component metal plating liquid according to claim 1, wherein the chloride ion has a molar concentration of between 0.1 and 3 mM.   The copper-silver two-component metal plating liquid according to claim 1, further comprising a thiourea compound; the thiourea compound is (R ₁ R ₂ N)(R ₃ R ₄ N)C= S, wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen or a hydrocarbon group of the same or different species.  The copper-silver two-component metal plating liquid according to claim 5, wherein the thiourea compound is thiourea, diethyl thiourea, phenylthiourea, allyl thiourea, diphenyl sulphur. Urea or one of the grouped groups.    The copper-silver two-component metal plating liquid according to claim 5 or 6, wherein the thiourea compound has a molar concentration of 5 to 10 times that of the silver methanesulfonate.    The copper-silver two-component metal plating liquid according to claim 1 or 5, further comprising a surfactant.    The copper-silver two-component metal plating liquid according to claim 8, wherein the surfactant is a polymer compound having a molecular weight of between 2,000 and 20,000.    The copper-silver two-component metal plating liquid according to claim 8, wherein the surfactant is polyethylene glycol, polypropylene glycol or a group thereof.    A copper-silver two-component metal plating method comprising the steps of: (a) contacting a copper-silver two-component metal plating liquid according to any one of claims 1 to 10; (b) applying a The working voltage is controlled to control the current density between 0.1 and 2 ASD to electroplate the substrate.    A copper-silver two-component metal plating layer prepared by a copper-silver two-component metal plating method according to claim 11 wherein the copper-silver two-component metal plating layer has a silver content of between 0.1 and 40% by weight. .