Substrate treatment method

Abstract

To provide a technique capable of forming a copper wiring while reducing an environmental load.SOLUTION: A copper wiring formation process includes: a film formation step S11; and a light irradiation step S12. The film formation step S11 is a step of forming a film 10 containing a copper nitride as a main component on a surface of a base material 9. A light irradiation step S12 is a step of selectively irradiating a film 10 with a laser light L1 to form a wiring containing a copper as a main component.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The subject matter disclosed herein relates to a method for treating a substrate. [Background technology]

[0002] In the process of forming fine wiring in semiconductor devices, a dual damascene process using copper plating is frequently used (for example, Patent Document 1). Cu plating is also used for TSVs (Through Silicon Vias) and redistribution lines (RDLs) that electrically connect semiconductor chips. Copper plating is also used for forming circuits on printed circuit boards.

[0003] There are various methods for forming circuits using copper plating, such as forming a plating layer over the entire surface of a substrate and then using photolithography to remove areas other than the circuit area, or forming a resist using photolithography and then forming a plating layer in the openings. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-356117 Summary of the Invention [Problem to be solved by the invention]

[0005] However, copper plating requires the use of a variety of chemicals in pre-treatment, post-treatment, etc. This poses a problem of increased environmental impact due to the use and disposal of a variety of chemicals.

[0006] An object of the present invention is to provide a technique that can form copper wiring while reducing the environmental load. [Means for solving the problem]

[0007] In order to solve the above problem, a first aspect is a substrate processing method for forming wiring on a substrate, which includes a film formation step of forming a film mainly composed of copper nitride on the surface of the substrate, and a light irradiation step of selectively irradiating the film with light to form wiring mainly composed of copper.

[0008] A second aspect is the substrate processing method of the first aspect, wherein the film forming step includes a step of forming the film on the surface of the substrate by sputtering.

[0009] A third aspect is a substrate treatment method according to the first or second aspect, wherein the substrate has a groove on its surface, the film formation process includes forming the film on at least the surface of the groove, and the light irradiation process includes selectively irradiating the film formed on the surface of the groove with light to form wiring mainly composed of copper on the surface of the groove.

[0010] A fourth aspect is the base material treatment method of the third aspect, further comprising, after the light irradiation step, an electrolytic plating step of forming a copper plating layer on the surface of the wiring by electrolytic plating.

[0011] A fifth aspect is the substrate treatment method of the first or second aspect, further comprising, after the light irradiation step, a film removal step of removing the film with an acid.

[0012] A sixth aspect is the substrate treatment method according to the first or second aspect, wherein the light irradiation step includes a step of irradiating with near-infrared light.

[0013] A seventh aspect is the method for treating a substrate according to the first or second aspect, wherein the film contains titanium or nickel.

[0014] An eighth aspect is the substrate treatment method of the first or second aspect, further comprising the step of: the film containing copper oxide. [Effects of the Invention]

[0015] According to the substrate treatment methods of the first to eighth aspects, the amount of chemicals used or discarded can be reduced compared to when copper wiring is formed by copper plating, thereby reducing the environmental load.

[0016] According to the base material processing method of the second aspect, productivity can be improved by using a sputtering method.

[0017] According to the base material treatment method of the third aspect, copper wiring can be formed in the grooves.

[0018] According to the fourth aspect of the substrate treatment method, the wiring containing copper as the main component can function as an electrode for electrolytic plating, so that a copper plating layer can be grown only on the surface of the wiring, thereby forming a thicker wiring.

[0019] According to the substrate treatment method of the sixth aspect, copper nitride can be efficiently thermally decomposed.

[0020] According to the substrate treatment method of the seventh aspect, the adhesion of the film can be improved.

[0021] According to the eighth aspect of the substrate treatment method, the decomposition temperature of copper nitride can be increased. [Brief explanation of the drawings]

[0022] [Figure 1] 3A to 3C are diagrams showing a flow of a copper wiring formation process according to the first embodiment. [Figure 2] 2A to 2C are diagrams schematically illustrating steps in the copper wiring formation process shown in FIG. 1. [Figure 3] 10A to 10C are diagrams showing the flow of a copper wiring formation process according to the second embodiment. [Figure 4] 4A to 4C are diagrams schematically illustrating the steps of the copper wiring formation process shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the components described in the embodiment are merely examples and are not intended to limit the scope of the present invention. In the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary to facilitate understanding.

[0024] 1. First embodiment FIG. 1 is a diagram showing the flow of a copper wiring formation process according to the first embodiment. FIG. 2 is a diagram showing each step of the copper wiring formation process shown in FIG. 1. The copper wiring formation process shown in FIGS. 1 and 2 is an example of a substrate processing method for forming copper wiring on a substrate 9. As the substrate 9, for example, a silicon substrate, a polyimide substrate, a free substrate, a ceramic substrate, or the like can be used. The substrate 9 may also be a film.

[0025] In this process, first, as shown in FIG. 2(a), a copper nitride film 10 is formed on the surface of a substrate 9 (FIG. 1: film formation step S11). Copper nitride has the composition formula CuN x A typical compound is nitrilotricopper(I) represented by the composition formula Cu3N (i.e., x=1 / 3). The film 10 is formed by, for example, sputtering.

[0026] As a sputtering method, for example, a reactive plasma sputtering method can be used. In the reactive plasma sputtering method, a substrate 9 is placed in a vacuum chamber, and a vacuum state is created. Then, a gas containing a sputtering gas (e.g., argon gas) and nitrogen gas as a reactive gas is introduced into the vacuum chamber, and the sputtering gas and nitrogen gas are turned into a plasma state by supplying power. Then, the surface of metallic copper as a target placed in the vacuum chamber is sputtered, and the copper target particles adhere to the surface of the substrate 9 together with the nitrogen reactive gas. As a result, a film 10 is formed on the surface of the substrate 9. The sputtering method allows the film 10 to be formed in a short time, thereby improving productivity.

[0027] The method for forming the film 10 is not limited to sputtering, but may be, for example, vacuum deposition or chemical vapor deposition (CVD).

[0028] The thickness of the film 10 is not particularly limited, but is, for example, 200 nm. By using a film formation method such as sputtering, it is possible to easily form a thinner film 10 than the copper film formed by copper plating.

[0029] After the film formation step S11, the film 10 on the base material 9 is selectively irradiated with light (FIG. 1: light irradiation step S12). Specifically, as shown in FIG. 2(b), a laser beam L1 is irradiated from a laser beam irradiation unit 21 onto a portion of the base material 9 where copper wiring is to be formed. That is, a circuit is directly drawn by laser irradiation.

[0030] The laser light L1 is light capable of decomposing copper nitride into nitrogen and copper, thereby reducing the copper nitride to copper. When copper nitride is heated to a certain temperature (e.g., 350°C) or higher, the nitrogen is released and the copper nitride is reduced to copper. By using a near-infrared laser with an absorption wavelength (700 cm-1 ≒ 14 μm) derived from the Cu-N bond in Cu3N as the laser light L1, the decomposition reaction of copper nitride can be efficiently promoted. Furthermore, the decomposition of copper nitride can be achieved by localized heating at 350°C or higher. For this reason, a laser with low heat generation, such as a pulsed laser, may be used as the laser light L1. By reducing the heat generation, fine-line circuits can be formed.

[0031] It should be noted that in the light irradiation step S12, it is not essential that the film 10 be heated to 350° C. or higher by the laser light L1. The laser light L1 may be any light having energy capable of breaking Cu—N bonds.

[0032] After the light irradiation step S12, the film 10 is removed (FIG. 1: film removal step S13). Specifically, the film 10 is removed by treatment with a non-oxidizing acid such as hydrochloric acid or dilute sulfuric acid. Although copper nitride is soluble in acids such as hydrochloric acid, copper is not corroded by non-oxidizing acids such as hydrochloric acid and dilute sulfuric acid. Therefore, as shown in FIG. 2(c), the film 10 can be removed from the substrate 9 by acid treatment while leaving the copper wiring 11 on the substrate 9.

[0033] Copper nitride is a dielectric and does not conduct electricity, so even if film 10 is left as is, copper wiring 11 can be used as an electric circuit. However, if there is a subsequent process in which base material 9 is heated to 350°C or higher (for example, a reflow process), it is desirable to remove film 10 in film removal step S13.

[0034] The copper wiring formation process of this embodiment can reduce the amount of chemicals used or disposed of compared to a copper wiring formation process using copper plating, thereby reducing the environmental impact.

[0035] Furthermore, by using a film formation method such as sputtering, the thickness of the copper nitride film 10 can be easily reduced compared to the thickness of copper film formed by copper plating. Therefore, even if the film 10 is removed by acid treatment, the amount of copper discarded is much less than that in the case of copper plating, thereby reducing the environmental load.

[0036] Furthermore, the copper wiring formation process using copper plating requires multiple photolithography steps, including resist application, exposure, and development. In contrast, the copper wiring formation process of this embodiment allows copper wiring to be formed by direct laser writing. Therefore, circuits can be formed in a shorter time than the copper wiring formation process using copper plating.

[0037] Furthermore, if the substrate 9 is a non-conductor, electrolytic plating, which is advantageous in terms of film formation rate and cost, cannot be applied, and therefore electroless plating must be selected. Electroless plating has a slow film formation rate, and the electroless plating process is more complicated than electrolytic plating, requiring advanced techniques and equipment, which can be costly. In contrast, according to the copper wiring formation process of this embodiment, the copper nitride film 10 can be formed by a simple method, such as sputtering, which is easy to mass-produce. Therefore, copper wiring can be formed in a short time and at low cost.

[0038] 2. Second embodiment Next, a second embodiment will be described. In the following description, elements having the same functions as elements already described will be given the same reference numerals or reference numerals with an additional alphabetical character, and detailed description thereof may be omitted.

[0039] Fig. 3 is a diagram showing the flow of a copper wiring formation process according to the second embodiment. Fig. 4 is a diagram showing each step of the copper wiring formation process shown in Fig. 3. The copper wiring formation process shown in Fig. 3 and Fig. 4 is a process of forming copper wiring in a wiring trench in which TSVs or the like are formed in order to form multilayer wiring, such as a damascene process.

[0040] In this copper wiring formation process, first, a wiring groove 91 is formed on the substrate 9 (FIG. 3: wiring groove formation step S21). The wiring groove 91 is formed by an insulating film 93, such as a silicon oxide film, which is a dielectric layer located on the surface of the substrate 9. The wiring groove 91 is formed by etching the insulating film 93. As shown in FIG. 4(a), the wiring groove 91 has a linearly extending recessed shape.

[0041] After the wiring groove forming step S21, a copper nitride film 10 is formed on the surface of the substrate 9 (FIG. 3: film forming step S22). The film 10 is formed by a sputtering method similar to that used in the film forming step S11 shown in FIG. 1. By this film forming step S22, the copper nitride film 10 is formed on at least the surface of the wiring groove 91, as shown in FIG. 4(b).

[0042] After the film formation step S22, the film 10 formed on the surface of the wiring groove 91 is selectively irradiated with light (FIG. 3: light irradiation step S23). Specifically, as shown in FIG. 4(c), laser light L1 is irradiated along the wiring groove 91, thereby reducing copper nitride on the surface of the wiring groove 91 to copper. As a result, copper wiring 11 is formed on the surface of the wiring groove 91.

[0043] After the light irradiation step S23, a copper plating layer 13 is formed by electrolytic plating (FIG. 3: electrolytic plating step S24). By the light irradiation step S23, copper wiring 11 is formed in the wiring groove 91, and the other portions are covered with insulating copper nitride. Therefore, in the electrolytic plating step S24, by making the copper wiring 11 in the wiring groove 91 function as an electrode, the copper plating layer 13 can be selectively grown in the wiring groove 91, and a thicker wiring can be formed.

[0044] In a typical damascene process, a copper plating layer is formed on the entire surface of the base material 9, and then unnecessary copper plating layer in areas other than the wiring grooves is removed by chemical mechanical polishing (CMP). In contrast, in the copper wiring formation process of this embodiment, the copper plating layer 13 can be selectively formed in the wiring grooves 91. Therefore, the amount of copper used can be significantly reduced compared to a typical damascene process.

[0045] Furthermore, because the copper nitride film 10 has insulating properties, it is possible to form the next layer of electrical circuits by leaving the film 10 as it is, without removing it. In this case, the formation of multilayer circuits can be completed in a shorter time than with a normal damascene process.

[0046] After the copper plating layer 13 is formed, the copper nitride film 10 may be removed by CMP. The thickness of the film 10 can be easily reduced compared to the thickness of copper in copper plating in a normal damascene process. Therefore, even when the film 10 is removed by CMP, the amount of copper waste can be reduced compared to a normal damascene process, thereby reducing the environmental load.

[0047] <3. Modifications> Although the embodiments have been described above, the present invention is not limited to the above and various modifications are possible.

[0048] For example, the film 10 formed in the film formation steps S11 and S22 may contain copper alloy nitrides such as CuTiN and CuNiN, with copper nitride as the main component. For example, in a sputtering method, the film 10 containing copper alloy nitrides can be formed by adding elements such as titanium (Ti) and nickel (Ni) to the sputtering target. In this way, by including copper alloy nitrides, the adhesion of the film 10 can be improved.

[0049] Furthermore, the film 10 formed in the film formation steps S11 and S22 may contain copper oxide. For example, in a sputtering method, the film 10 containing copper oxide can be formed by mixing oxygen gas with nitrogen gas. In this way, by making the film 10 contain copper oxide, the decomposition temperature of the film 10 can be increased.

[0050] Although the present invention has been described in detail, the above description is merely illustrative in all respects and does not limit the present invention. It is understood that countless variations not illustrated can be envisioned without departing from the scope of the present invention. The configurations described in the above embodiments and variations can be combined or omitted as appropriate as long as they are not mutually inconsistent. [Explanation of symbols]

[0051] 9: Base material 10 : Membrane 11: Copper wiring 13: Copper plating layer 91: Wiring groove L1: Laser light

Claims

1. A substrate processing method for forming wiring on a substrate, comprising: a film forming step of forming a film containing copper nitride as a main component on the surface of the substrate; a light irradiation step of selectively irradiating the film with light to form wiring mainly composed of copper; A method for treating a substrate, comprising:

2. The substrate processing method according to claim 1, The film forming step includes a step of forming the film on the surface of the substrate by a sputtering method.

3. The substrate treatment method according to claim 1 or 2, the substrate has a groove on its surface, the film forming step includes a step of forming the film on at least the surface of the groove, The light irradiation step includes a step of selectively irradiating the film formed on the surface of the groove with light to form wiring mainly composed of copper on the surface of the groove.

4. The substrate processing method according to claim 3, an electrolytic plating step of forming a copper plating layer on the surface of the wiring by electrolytic plating after the light irradiation step; The method of treating a substrate further comprises:

5. The substrate treatment method according to claim 1 or 2, a film removal step of removing the film with acid after the light irradiation step; The method of treating a substrate further comprises:

6. The substrate treatment method according to claim 1 or 2, The light irradiation step includes a step of irradiating with near-infrared light.

7. The substrate treatment method according to claim 1 or 2, The method for treating a substrate, wherein the film comprises titanium or nickel.

8. The substrate treatment method according to claim 1 or 2, The film comprises copper oxide. The substrate processing method further comprises:

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