Method for forming metal interconnection and metal interconnection structure

Abstract

The invention provides a method for forming metal interconnection and a metal interconnection structure, which can improve the electromigration resistance of a metal layer, improve the device performance and improve the product yield. In order to solve the problem, the invention provides a method for forming metal interconnection, which comprises the following steps of: providing a substrate; forming a titanium-nitrogen alloy layer on the surface of the substrate; carrying out oxidation treatment on the surface of the titanium-nitrogen alloy layer; and forming an aluminum metal layer on the oxidized surface. According to the technical scheme, Ti enriched on the surface of the titanium-nitrogen alloy layer is oxidized through the oxidation step, the crystal orientation is converted from the {002} crystal orientation to the {111} crystal orientation, it is guaranteed that the surface of the grown aluminum metal layer is the {111} crystal orientation, and the aluminum metal layer grown in the crystal orientation in an induced mode also inherits the {111} crystal orientation. And the aluminum metal layer with the {111} crystal orientation has better electromigration resistance, so that the performance of the device is improved, and the product yield is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for forming metal interconnection and a metal interconnection structure. Background Art

[0002] Electromigration is one of the main failure mechanisms for the reliability of interconnects in microelectronic devices. It can cause open circuits and short circuits in metallization, increasing the leakage current of the device. Metals are crystals. Metal ions are arranged in order inside the crystal. When no external electric field is applied, the metal ions change positions through vacancies in the lattice. This is called the self-diffusion movement of metal ions. This movement occurs randomly. Any ion close to an adjacent vacancy has the same probability of exchanging positions with the vacancy, so self-diffusion does not cause mass transport. However, when the metal is used as a conductor to conduct direct current, the electric field drives the electrons to move from the cathode to the anode. The high-speed moving electrons continuously exchange energy with the metal atoms, and the atoms are subjected to a violent electron impact force. This is the so-called electron wind. Driven by the electron wind, the metal ions diffuse directionally from the cathode to the anode through the vacancies. This is electromigration. Therefore, how to improve the anti-electromigration ability of the metal layer is a problem that the existing technology needs to solve. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for forming metal interconnection and a metal interconnection structure, which can improve the anti-electromigration capability of the metal layer, improve device performance, and increase product yield.

[0004] In order to solve the above problems, the present invention provides a method for forming metal interconnection, comprising the following steps: providing a substrate; forming a titanium-nitrogen alloy layer on the surface of the substrate to form titanium oxide with a {111} crystal orientation; oxidizing the surface of the titanium-nitrogen alloy layer; and forming an aluminum metal layer on the oxidized surface.

[0005] Optionally, the oxidation treatment temperature range is 250-400° C., the O2 flow rate used for oxidation is 3000-5000 standard liters / minute, and the time is 80-120 seconds.

[0006] Optionally, the titanium oxide is in cluster morphology.

[0007] Optionally, the substrate surface has an insulating layer, and the insulating layer surface has a titanium metal layer.

[0008] Optionally, the method further comprises: continuing to form an anti-reflection layer on the surface of the aluminum metal layer; the anti-reflection layer is a titanium / titanium nitride composite layer.

[0009] In order to solve the above problems, the present invention provides a metal interconnection structure, comprising: a substrate; a titanium-nitrogen alloy layer on the surface of the substrate; an aluminum metal layer on the surface of the titanium-nitrogen alloy layer, and titanium oxide material is provided between the titanium-nitrogen alloy layer and the aluminum metal layer.

[0010] Optionally, the substrate surface has an insulating layer, and the insulating layer surface has a titanium metal layer.

[0011] Optionally, the titanium oxide material is in cluster morphology.

[0012] Optionally, an anti-reflection layer is further included on the surface of the aluminum metal layer; the anti-reflection layer is a titanium / titanium nitride composite layer.

[0013] The oxidation step in the above technical solution oxidizes the Ti enriched on the surface of the titanium-nitrogen alloy layer, and the crystal orientation is transformed from the {002} crystal orientation to the {111} crystal orientation, ensuring that the surface of the growing aluminum metal layer is the {111} crystal orientation, and the aluminum metal layer induced to grow in this crystal orientation also inherits the {111} crystal orientation. The aluminum metal layer with the {111} crystal orientation has better anti-electromigration ability, thereby improving device performance and product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following is a brief introduction to the drawings required for the description of the specific embodiments. Obviously, the drawings described below are only some specific embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0015] Attached Figure 1 Shown is a schematic diagram of the steps of a method for forming metal interconnections according to a specific embodiment of the present invention.

[0016] Attached Figure 2A To Attachment Figure 2D Shown is a process schematic diagram of a method for forming metal interconnections according to a specific embodiment of the present invention.

[0017] Attached Figure 3 Shown is a comparison of SEM photographs of the surface morphology of aluminum metal using the above technical solution. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the specific embodiments of the present invention to clearly and completely describe the technical solutions in the specific embodiments of the present invention. Obviously, the specific embodiments described are only part of the specific embodiments of the present invention, not all of the specific embodiments. Based on the specific embodiments of the present invention, all other specific embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] The following is a detailed description of the method for forming metal interconnection and the specific implementation of the metal interconnection structure provided by the present invention in conjunction with the accompanying drawings.

[0020] Attached Figure 1 The figure is a schematic diagram of the steps of a method for forming metal interconnection according to a specific embodiment of the present invention, comprising the following steps: step S10, providing a substrate; step S11, forming a titanium-nitrogen alloy layer on the surface of the substrate; step S12, oxidizing the surface of the titanium-nitrogen alloy layer; step S13, forming an aluminum metal layer on the oxidized surface; step S14, continuing to form an anti-reflection layer on the surface of the aluminum metal layer.

[0021] Attached Figure 2A To Attachment Figure 2D Shown is a process schematic diagram of a method for forming metal interconnections according to a specific embodiment of the present invention.

[0022] Attached Figure 2AAs shown, referring to step S10, a substrate 10 is provided. The substrate 10 may be a single crystal semiconductor wafer. In one embodiment, the substrate 10 is a semiconductor wafer, and is selected from a material of the group consisting of silicon, silicon carbide, silicon germanium, gallium arsenide, gallium nitride, indium phosphide, indium gallium arsenide, germanium and a combination thereof. In this embodiment, the surface of the substrate 10 has an insulating layer 11, and the surface of the insulating layer 11 has a titanium metal layer 12. In some embodiments, the insulating layer 11 can be deposited by plasma technology, including a semiconductor nitride (e.g., silicon nitride) layer, a semiconductor nitride oxide (e.g., silicon oxynitride) layer and a semiconductor oxide (e.g., silicon oxide) layer. In other embodiments, the material of the insulating layer 11 may also be silicon nitride, silicon oxynitride, and any common semiconductor material that can play an insulating role, such as an insulating material selected from hafnium oxide, titanium oxide, zirconium oxide, lanthanum oxide, barium oxide and any combination thereof. The surface of the substrate 10 may have an integrated circuit formed by any one or a combination of capacitors, resistors, transistors, etc. The subsequent metal interconnection structure is used to form electrical interconnection between these electronic components, or to form electrical interconnection between the integrated circuit formed by these electronic components and the outside world. The role of the insulating layer 11 is to support the subsequent metal interconnection structure, ensure the electrical isolation between the metal interconnection structure and the substrate components, and the electrical isolation between the metal interconnections. The role of the titanium metal layer 12 is adhesion.

[0023] Attached Figure 2BAs shown, referring to step S11, a titanium-nitrogen alloy layer 13 is formed on the surface of the substrate 10. In this specific embodiment, the titanium-nitrogen alloy layer 13 is formed on the surface of the titanium metal layer 12, that is, an alloy layer composed of two elements Ti and N is formed on the surface of the titanium metal layer 12 by epitaxy, evaporation, sputtering and other processes, and the formation process includes physical vapor deposition (PVD), chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), or plasma enhanced chemical vapor deposition (PECVD) deposition, etc. The titanium-nitrogen alloy layer 13 and the titanium metal layer 12 have similar functions, both for better adhesion between the subsequent metal interconnect structure and the insulating layer 11. Ideally, the number of Ti and N atoms is the same, that is, a TiN layer is formed. However, in the actual process, due to the limitation of the growth process, the Ti atoms will be slightly more than the N atoms, and a Ti-rich titanium-nitrogen alloy layer 13 is formed on the surface of the titanium metal layer 12. It has been found that the Ti-rich situation will bring technical problems. Because the crystal orientation of titanium is {002}, and the crystal orientation of TiN itself is {111}. However, the adhesion layer TiN is not a pure TiN structure. During the process of this layer, Ti will be doped into it to form a Ti-rich layer. The actual crystal orientation of titanium nitride is a mixed crystal orientation of titanium {002} and TiN {111}. The {002} crystal orientation problem of titanium will cause the subsequent Al crystal to be uneven, forming a large number of amorphous and grain boundaries. In the interconnect structure of integrated circuits using the Al interconnect system, Al is a polycrystalline structure, so the migration path of ions mainly has three diffusion modes: lattice diffusion, inter-grain boundary diffusion and surface diffusion. If Al metal cannot grow consistently in the {111} crystal orientation, it will inevitably affect the diffusion efficiency. Al with the {111} crystal orientation is the most stable crystal orientation, which can have a more stable metal structure and can effectively reduce the diffusion path of metal ions. This situation will cause the subsequent Al metal interconnect structure to be unstable.

[0024] Step S12, oxidizing the surface of the titanium-nitrogen alloy layer 13. In this step, titanium oxide with a {111} crystal orientation is formed on the surface of the titanium-nitrogen alloy layer 13. In order to solve the above-mentioned technical problems, the technical solution adopted in this specific embodiment is to oxidize the surface of the titanium-nitrogen alloy layer 13. The oxidation treatment temperature range is 250-400°C, and preferably 300°C. The heating step can be to place the substrate 10 on a heating plate and heat the heating plate to the target temperature. Since the thickness of the substrate 10 is very thin, usually about 500μm, the temperature of the substrate 10 is the same as the temperature of the heating plate. The O2 flow rate used for oxidation is 3000-5000 standard liters / minute (sccm), and the upper introduction method or parallel airflow method can be adopted, and N2 or inert gas can be used as a carrier gas to adjust the oxidation speed. The oxidation treatment time is 80-120 seconds. After an appropriate oxidation duration, the chamber can be cooled to a safe temperature for removing the substrate 10. Oxidation treatment can oxidize the enriched Ti to form titanium oxide. In the presence of sufficient oxygen, the reaction equation is: Ti+O2→TiO2, and the product is TiO2. In this step, since the Ti element is enriched relative to N, the TiO2 on the surface may not form a continuous film structure, but may be dispersed crystal clusters rather than a continuous film, so it is not marked in the figure. Whether it is a continuous film structure or a dispersed cluster, the main crystal orientation of TiO2 is consistent with that of TiN, which is the {111} crystal orientation. Therefore, the {002} crystal orientation in TiN can be converted into the {111} crystal orientation, helping Al to grow toward the {111} crystal orientation, thereby improving the ability to resist electromigration, improving device performance, and increasing product yield.

[0025] Attached Figure 2C As shown, referring to step S13, an aluminum metal layer 14 is formed on the surface after oxidation treatment. The surface after oxidation treatment is a titanium oxide layer, and the aluminum metal layer 14 is formed on its surface by epitaxy, evaporation, sputtering and other processes, and the processes used include physical vapor deposition (PVD), chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), or plasma enhanced chemical vapor deposition (PECVD) deposition, etc. Due to the oxidation effect of the previous step, the Ti enriched on the surface of TiN is oxidized, and the crystal orientation is transformed from the {002} crystal orientation to the {111} crystal orientation, ensuring that the surface of the growing aluminum metal layer 14 is the {111} crystal orientation, and the Al metal layer induced to grow on this crystal orientation also inherits the {111} crystal orientation. The aluminum metal layer 14 with the {111} crystal orientation has better resistance to electromigration, thereby improving device performance and increasing product yield.

[0026] Attached Figure 3The SEM images of the surface morphology of the aluminum metal layer 14 using the above technical solution are shown. Part (a) is the surface morphology of Al formed directly on the TiN surface without using step S12, and part (b) is the surface morphology after oxidation using step S12. The comparison shows that the latter has fewer grain boundaries, a smoother surface, and a higher proportion of {111} crystal orientation.

[0027] Attached Figure 2D As shown, referring to step S14, an anti-reflection layer 15 is further formed on the surface of the aluminum metal layer 14. This step is an optional step. The anti-reflection layer 15 is preferably a titanium / titanium nitride composite layer. The function of the anti-reflection layer is to reduce the reflectivity of the Al surface in subsequent processes such as photolithography, which is more conducive to the subsequent processes.

[0028] In a specific embodiment, after the above process is implemented, a metal interconnection structure is formed, including: a substrate 10; an optional insulating layer 11 and a titanium metal layer 12 on the surface of the substrate 10; a titanium-nitrogen alloy layer 13 on the surface of the titanium metal layer 12; and an aluminum metal layer 14 on the surface of the titanium-nitrogen alloy layer 13. There is a titanium oxide material between the titanium-nitrogen alloy layer and the aluminum metal layer, and the titanium oxide material is preferably in a cluster morphology. In a specific embodiment, the surface of the aluminum metal layer also includes an anti-reflection layer 15. The anti-reflection layer 15 is a titanium / titanium nitride composite layer.

[0029] In one embodiment, the substrate 10 may be a single crystal semiconductor wafer. In one embodiment, the substrate 10 is a semiconductor wafer, and is a material selected from the group consisting of silicon, silicon carbide, silicon germanium, gallium arsenide, gallium nitride, indium phosphide, indium gallium arsenide, germanium and combinations thereof. In this embodiment, the surface of the substrate 10 has an insulating layer 11, and the surface of the insulating layer has a titanium metal layer 12. The material of the insulating layer 11 is preferably SiO2. The material of the insulating layer 11 may also be silicon nitride, silicon oxynitride, and any common semiconductor material that can play an insulating role, such as an insulating material selected from hafnium oxide, titanium oxide, zirconium oxide, lanthanum oxide, barium oxide and any combination thereof.

[0030] In a specific embodiment, the surface of the titanium-nitrogen alloy layer 13 is oxidized at a temperature of 250-400° C., preferably 300° C., with an O2 flow rate of 3000-5000 standard liters per minute (sccm) for 80-120 seconds.

[0031] The crystal orientation of titanium is {002}, and the crystal orientation of TiN itself is {111}. However, the adhesion layer TiN is not a pure TiN structure. During the process of this layer, Ti will be doped to form a Ti-rich layer. The actual crystal orientation of titanium nitride is a mixed crystal orientation of titanium {002} and TiN {111}. The problem of titanium {002} crystal orientation will cause the subsequent Al crystal to be uneven, forming a large number of amorphous and grain boundaries. In the interconnect structure of integrated circuits using the Al interconnect system, Al is a polycrystalline structure, so the migration path of ions mainly includes three diffusion modes: lattice diffusion, inter-grain boundary diffusion and surface diffusion. If Al metal cannot grow consistently in the {111} crystal orientation, it will inevitably affect the diffusion efficiency. Al with the {111} crystal orientation is the most stable crystal orientation, which can have a more stable metal structure and can effectively reduce the diffusion path of metal ions. This situation will cause the subsequent Al metal interconnect structure to be unstable.

[0032] The oxidation treatment can oxidize the Ti enriched on the surface of the titanium-nitrogen alloy layer 13 to form titanium oxide. In the case of sufficient oxygen, the reaction equation is: Ti+O2→TiO2, and the product is TiO2. Since the Ti element is enriched relative to N, the TiO2 on the surface may not form a continuous film structure, and it may also be a dispersed crystal cluster rather than a continuous film, so it is not marked in the figure. Whether it is a continuous film structure or a dispersed cluster, the main crystal orientation of TiO2 is consistent with TiN, which is the {111} crystal orientation. Therefore, the {002} crystal orientation in TiN can be converted into the {111} crystal orientation, which helps Al to grow toward the {111} crystal orientation, thereby improving the anti-electromigration capability, improving the device performance, and improving the product yield.

[0033] It should be noted that references in the specification to "an embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, whether or not explicitly described, it is within the knowledge of a technician in the relevant art to implement such feature, structure, or characteristic in conjunction with other embodiments.

[0034] Typically, a term can be understood at least in part from usage in context. For example, the term "one or more" as used herein depends at least in part on the context and can be used to describe any feature, structure or characteristic in a singular sense, or can be used to describe a combination of features, structures or features in a plural sense. Similarly, terms such as "one", "a" or "the" can also be understood to express singular usage or to express plural usage, depending at least in part on the context. In addition, the term "based on" can be understood to not necessarily be intended to express a set of exclusive factors, but can alternatively, also at least in part depending on the context, allow for the presence of other factors that are not necessarily explicitly described. It should also be noted in this specification that "connected / coupled" refers not only to the direct coupling of one component to another component, but also to the indirect coupling of one component to another component through an intermediate component.

[0035] It should be noted that the terms "including" and "having" and their variations involved in the documents of the present invention are intended to cover non-exclusive inclusions. The terms "first", "second", etc. are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. Unless the context clearly indicates otherwise, it should be understood that the data used in this way can be interchanged under appropriate circumstances. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other unless there is a conflict. In addition, in the above description, the description of well-known components and technologies is omitted to avoid unnecessary confusion of the concepts of the present invention. In the above embodiments, each embodiment focuses on the differences from other embodiments, and the same / similar parts between the embodiments can be referred to each other.

[0036] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for forming a metal interconnection, It is characterized in that The steps include: providing a substrate; forming a titanium-nitrogen alloy layer on the surface of the substrate; performing oxidation treatment on the surface of the titanium-nitrogen alloy layer to form titanium oxide having a {111} crystal orientation; An aluminum metal layer is formed on the surface after oxidation treatment.

2. The method according to claim 1, It is characterized in that The oxidation treatment temperature range is 250-400°C, and the oxidation temperature is O 2 The flow rate is 3000-5000 standard liters / minute, and the time is 80-120 seconds.

3. The method according to claim 1, It is characterized in that The titanium oxide is in cluster morphology.

4. The method according to claim 1, It is characterized in that The substrate surface has an insulating layer, and the insulating layer surface has a titanium metal layer.

5. The method according to claim 1, It is characterized in that The method further includes: continuously forming an anti-reflection layer on the surface of the aluminum metal layer.

6. The method according to claim 5, It is characterized in that The anti-reflection layer is a titanium / titanium nitride composite layer.

7. A metal interconnect structure, It is characterized in that include: substrate; A titanium-nitrogen alloy layer on the surface of the substrate; An aluminum metal layer is disposed on the surface of the titanium-nitrogen alloy layer, and titanium oxide material is disposed between the titanium-nitrogen alloy layer and the aluminum metal layer.

8. The structure according to claim 7, It is characterized in that The substrate surface has an insulating layer, and the insulating layer surface has a titanium metal layer.

9. The structure according to claim 7, It is characterized in that The titanium oxide material is in cluster morphology.

10. The structure according to claim 7, It is characterized in that An anti-reflection layer is also included on the surface of the aluminum metal layer.

11. The structure according to claim 10, It is characterized in that The anti-reflection layer is a titanium / titanium nitride composite layer.

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