Integrated etching method

Abstract

This application discloses an integrated etching method, comprising: performing integrated etching to form a groove in a metal layer and a first dielectric layer, the first dielectric layer being formed on a second dielectric layer, and a metal line being formed in the second dielectric layer, with the metal line exposed at the bottom of the groove, the metal line and the metal layer containing different materials; performing post-etching to remove the fluorocarbon polymers generated during the integrated etching, the post-etching comprising three etching stages: in the first etching stage, a reactive gas including carbon monoxide and / or carbon dioxide is introduced; in the second etching stage, a reactive gas including hydrogen and an inert gas is introduced; and in the third etching stage, a reactive gas including carbon monoxide and / or carbon dioxide is introduced. By adding an etching stage containing a reactive gas including hydrogen and an inert gas during the post-etching process of integrated etching, this application can reduce the formation of residual metal fluoride compounds, thereby improving the reliability and yield of the device product.

Description

Technical Field

[0001] This application relates to the field of semiconductor devices and integrated circuit technology, and in particular to an integrated etching method. Background Technology

[0002] In the back-end of line (BEOL) process of semiconductor integrated circuit manufacturing, metal interconnect structures are typically formed to bring out the electrodes in the device. During the formation of the metal interconnect structure, an all-in-one (AIO) etching process is used to open multiple thin film layers made of different materials to form grooves (or vias).

[0003] In related technologies, in integrated etching processes, the etching of oxide dielectric materials generally uses fluorine-containing gases (e.g., carbon tetrafluoride (CF4), octafluorocyclobutane (C4F8), etc.) as the main etching gas. During the etching process, a significant amount of fluorocarbon polymers (C4F8) are formed. x F y The polymer (where x and y are natural numbers, x≥1, y≥1) is adsorbed onto the sidewall of the groove for protection.

[0004] However, if the polymer generated during the etching process cannot be completely removed after etching, the residual polymer is prone to react with water vapor and hydrolyze, releasing fluoride ions. These ions then react with the metal in the metal hard mask to form metal fluorides. If they combine with oxygen ions, they can easily form non-volatile metal fluoride oxides (MOFs, where M is a metal element) that remain, which can easily cause some via open defects, especially in smaller node processes, thereby reducing the reliability and yield of device products. Summary of the Invention

[0005] This application provides an integrated etching method that solves the problem that integrated etching methods in related technologies easily produce non-volatile residues. The method includes: An integrated etching process is performed to form a groove in a metal layer and a first dielectric layer. The first dielectric layer is formed on a second dielectric layer, and a metal line is formed in the second dielectric layer. The metal line at the bottom of the groove is exposed, and the metal line and the metal layer contain different materials. Post-etching removes the fluoropolymers generated during the integrated etching process. The post-etching process includes three etching stages: in the first etching stage, the reactant gas introduced includes carbon monoxide and / or carbon dioxide; in the second etching stage, the reactant gas introduced includes hydrogen and an inert gas; and in the third etching stage, the reactant gas introduced includes carbon monoxide and / or carbon dioxide.

[0006] In some embodiments, the metal layer comprises a titanium nitride layer, and the metal line comprises a copper layer.

[0007] In some embodiments, the first dielectric layer comprises, from bottom to top, an NDC layer and a ULK layer.

[0008] In some embodiments, the second dielectric layer includes a silicon dioxide layer.

[0009] In some embodiments, the inert gas includes nitrogen.

[0010] In some embodiments, during the second etching stage, the hydrogen flow rate is 0 to 100 SCCM.

[0011] In some embodiments, during the second etching stage, the nitrogen flow rate is 0 to 400 SCCM.

[0012] In some embodiments, during the second etching stage, the reaction is controlled by high-frequency power and low-frequency power, respectively.

[0013] In some embodiments, during the second etching stage, the power of the high-frequency power is greater than the power of the low-frequency power.

[0014] The technical solution of this application has at least the following advantages: By adding an etching stage containing hydrogen and inert gas in the post-etching process of integrated etching, hydrogen can reduce oxygen in metal fluoride oxide residues into volatile metal fluorides, which are then carried away by the introduced inert gas through a vacuum pump. At the same time, hydrogen can suppress the activity of oxygen, thereby reducing the formation of metal fluoride oxide residues. This reduces the perforation defects caused by metal fluoride oxide residues to a certain extent, improving the reliability and yield of device products. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a flowchart of an integrated etching method provided in an exemplary embodiment of this application; Figures 2 to 4 This is a schematic diagram of the etching process of an integrated etching method provided in an exemplary embodiment of this application. Detailed Implementation

[0017] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection between two components; and they can refer to wireless connections or wired connections. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0021] refer to Figure 1 It illustrates a flowchart of an integrated etching method provided in an exemplary embodiment of this application, such as... Figure 1 As shown, the method includes: Step S1: Perform integrated etching to form a groove in the metal layer and the first dielectric layer. The first dielectric layer is formed on the second dielectric layer. Metal lines are formed in the second dielectric layer. The metal lines at the bottom of the groove are exposed. The metal lines and the metal layer contain different materials.

[0022] refer to Figure 2 It shows a cross-sectional schematic diagram before integrated etching; Reference Figure 3 This illustrates a cross-sectional view after integrated etching. For example, such as... Figure 2 and Figure 3 As shown, a substrate used to form a semiconductor device ( Figures 2 to 4A second dielectric layer 211 is formed on the substrate (not shown in the image), a metal line 300 is formed in the second dielectric layer 211, a first dielectric layer 212 is formed on the second dielectric layer, and a metal layer 213 is formed on the first dielectric layer 212. The metal line 300 and the metal layer 213 contain different materials.

[0023] Photoresist can be covered in metal layer 213. Figure 2 and Figure 3 (Not shown in the image) The photoresist in the target area (the area corresponding to the groove 400, which is located above the metal line 300 and whose width is less than the width of the metal line 300) is removed sequentially by exposure and development. Integrated etching is performed to remove the metal layer 213 and the first dielectric layer 212 in the target area until the metal line 300 is exposed. The groove 400 is formed in the metal layer 213 and the first dielectric layer 212. The width W of the groove 400 is less than its depth H. The reaction gas introduced in the integrated etching includes fluorine-containing gas. After integrated etching, fluoropolymers remain in the groove 400.

[0024] Taking a metal line 300 containing a copper (Cu) layer and a metal layer 213 containing a titanium nitride (TiN) layer as an example, the structure of the embodiment of this application will be described. Optionally, the first dielectric layer 212 includes, from bottom to top, a nitride-doped silicon carbide (NDC) layer 2121 and an ultra-low-k (ULK) layer 2122, the thickness of which is greater than that of the NDC layer 2121. The ULK layer 2122 is a thin film layer with a dielectric constant k less than 4; for example, it can be a porous carbon-doped silicon oxide (SiCOH) layer. The ULK layer is a porous material layer formed by reacting a silicon (Si)-based compound with organic matter in a chemical vapor deposition (CVD) process to form a composite material, followed by removing the organic matter from the composite material using an ultraviolet process.

[0025] Step S2 involves post-etching to remove the fluoropolymers generated during the integrated etching process. The post-etching process includes three etching stages: in the first etching stage, the introduced reaction gases include carbon monoxide and / or carbon dioxide; in the second etching stage, the introduced reaction gases include hydrogen and an inert gas; and in the third etching stage, the introduced reaction gases include carbon monoxide and / or carbon dioxide.

[0026] In this embodiment of the application, in the two stages of post-etch treatment (PET), an etching stage is added in which hydrogen (H2) and inert gases (nitrogen (N2), argon (Ar), helium (He), etc.) are introduced. Hydrogen can reduce the oxygen in the metal fluoride oxide residue to volatile metal fluorides, which are then carried away by the introduced inert gas through a vacuum pump. At the same time, hydrogen can suppress the activity of oxygen, thereby reducing the formation of metal fluoride oxide residue.

[0027] Taking an example where the metal line includes a copper layer, the metal layer includes a titanium nitride layer, and the inert gas includes nitrogen: In post-etching, the fluoropolymer reacts with water vapor (H2O) to form a non-volatile titanium fluoride condensate (TiOFH). The relevant chemical equation is as follows: 4F + H₂O → 4HF + O₂ HF + TiO → TiOFH In the second etching stage, after hydrogen and nitrogen are introduced, the hydrogen reacts with the fluorine-titanium condensate to form volatile titanium fluoride compounds (TiF). The relevant chemical equation is as follows: TiOF + H₂ → TiF + H₂O H₂ + O → H₂O Optionally, in the second etching stage, the hydrogen flow rate is 0 to 100 standard cubic centimeters per minute (SCCM), and the nitrogen flow rate is 0 to 400 SCCM. In the second etching stage, the reaction is controlled by high-frequency power and low-frequency power, with the high-frequency power (ranging from 0 to 200 watts) being greater than the low-frequency power (ranging from 0 to 100 watts). A schematic diagram of the cross-section after etching is shown below. Figure 4 As shown, there are no metal fluorine oxide residues in groove 400.

[0028] In summary, in the embodiments of this application, by adding an etching stage containing a reactive gas including hydrogen and an inert gas in the post-etching process of integrated etching, hydrogen can reduce oxygen in the metal fluoride oxide residue to volatile metal fluorides, which are then carried away by the introduced inert gas through a vacuum pump. At the same time, hydrogen can suppress the activity of oxygen, thereby reducing the generation of metal fluoride oxide residues, which to a certain extent reduces the perforation defects caused by metal fluoride oxide residues and improves the reliability and yield of device products.

[0029] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. An integrated etching method, characterized in that, include: An integrated etching process is performed to form a groove in a metal layer and a first dielectric layer. The first dielectric layer is formed on a second dielectric layer, and a metal line is formed in the second dielectric layer. The metal line at the bottom of the groove is exposed, and the metal line and the metal layer contain different materials. Post-etching removes the fluoropolymers generated during the integrated etching process. The post-etching process includes three etching stages: in the first etching stage, the reactant gas introduced includes carbon monoxide and / or carbon dioxide; in the second etching stage, the reactant gas introduced includes hydrogen and an inert gas; and in the third etching stage, the reactant gas introduced includes carbon monoxide and / or carbon dioxide.

2. The method according to claim 1, characterized in that, The metal layer includes a titanium nitride layer, and the metal wire includes a copper layer.

3. The method according to claim 2, characterized in that, The first dielectric layer comprises, from bottom to top, an NDC layer and a ULK layer.

4. The method according to claim 3, characterized in that, The second dielectric layer includes a silicon dioxide layer.

5. The method according to any one of claims 1 to 4, characterized in that, The inert gas includes nitrogen.

6. The method according to any one of claims 5, characterized in that, During the second etching stage, the hydrogen flow rate is 0 to 100 SCCM.

7. The method according to claim 6, characterized in that, During the second etching stage, the nitrogen flow rate is 0 to 400 SCCM.

8. The method according to claim 7, characterized in that, In the second etching stage, the reaction is controlled by high-frequency power and low-frequency power, respectively.

9. The method according to claim 8, characterized in that, In the second etching stage, the power of the high-frequency power is greater than the power of the low-frequency power.

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